Wednesday, December 25, 2019

Audio-technica BPHS-1 and Icom

I received a Audio-technica BPHS-1 headset for Christmas from my wife :-) The BPHS-1 looks to be a quality headset that is well rated on Amazon, Audio-technica's site and other places.

K8JHR wrote an article called Headsets I have tried, like or recommend which includes the BPHS-1.

I quickly discovered that Icom rigs (and Elecraft) are setup for electret condenser microphones, where as the rest use dynamic microphones. Electret mics are powered, dynamic mics are not and are about 20 dB lower in level. The BPHS-1 uses a dynamic mic.

Will a dynamic mic work with an Icom? Maybe..


Next, cables. The BPHS-1 comes with a cable that has a 1/4" plug for the headphones and a 3-pin XLRM-type connector for the mic.

  • First, the mic pin in an Icom supplies 8 VDC for the electret mics they use, when used with a dynamic mic we need to use a DC blocking capacitor otherwise the magic smoke will come out. Heil recommends a 1 uF tantalum (noted in heilsound.com link above), some posts on QRZ suggest anything up-to 10 uF is good. I found some 2.2 uF 16V tantalum capacitors on Amazon, these are polarized so the positive leg should connect to the mic pin in the Icom.
  • Mic side: Need a female 3-pin XLRM, I chose this cable from Amazon, can cut to length and wire into a 8-pin Foster mic plug with the DC blocking cap for the Icom's mic socket.
  • Headphone side: 1/4" to 3.5mm adapters are easy to find, thou I prefer a short cable here so the 3.5mm jack in the rig doesn't have an adapter and 1/4" plug hanging out of it. A quick search around Amazon finds MillSO 1/4 to 3.5mm Headphone Adapter, TRS 6.35mm Female to 3.5mm Male 1ft cable.
  • A cheaper option is to just cut the 1/4" and 3-pin XRLM plugs off, put a 3.5mm plug on the headphone side, and 8-pin Foster mic plug on the other plus the DC blocking cap.

Parts ordered, plan to have it together next week..

Parts arrived yesterday 29 Dec, I installed the DC blocking cap into the mic plug, I found I could fit it in-between the unused pins:




I cut the XLRM cable so it matched the 1/4" to 3.5 mm adapter cable length, and it looks like this:




Wiring diagram: Headset diagram from BPHS-1 manual (left), the mic connector diagram is from my Icom IC-7300 manual (right), with the connections shown as I wired it:



The shield (shown in green) I folded back in the mic plug and "clamped" in with the strain relief so it's grounded to the frame of the radio via the plug.

After adjusting the mic gain and compressor settings on SSB, I found mic gain at 80% and compressor at 5 would drive the IC-7300 about the same as the supplied hand mic with mic gain at 40% and compressor off. I did this by doing several comparisons watching the RF power output and listening to my self via the rigs monitor function with the headset on.

I have yet to do an on air test on SSB. I was able to do a quick test on a 6 m FM repeater, on FM the speech compressor option is unavailable and with the mic gain set to 100% the deviation is too low.

Sunday, December 22, 2019

AL-80B Keying Interface

KV5R wrote a nice article (Amp Interface) on building a solid state keying / relay interface for use with Icom rigs, using an SPST-NO MOSFET switch. I also have an Icom rig and an Ameritron AL-80B.

The nice thing about this is it's super simple, much faster than a mechanical relay and is opto-isolated.

I had ordered some parts for another project a while back, part of which was to rebuild the keying interface so I could key two devices. That project got shelved, but today I decided to rebuild the interface as originally planned since I had the stuff to do it.

Version 1 (with the heat shrink removed):


I had this hanging out the back of the rig, that was ok.

Version 2:




Only the orange and grey wires are used from the Icoms pigtail, the rest are just tucked out of the way.

The solid state switch's control voltage is 3 to 10V, but work ok from 12V. With two of them I wired them series for use with the rigs accessory jack which supplies 12V when keyed. With this I can independently key two separate devices with a closing current of 3A at up-to 60V each.

Parts I used:
  • Project box is a "Zulkit Waterproof Plastic Project Box ABS IP65 Electronic Junction box Enclosure Black 3.94 x 2.68 x 1.97 inch (100X68X50mm) (Pack of 2)", from Amazon. I have found it quite difficult to find good project boxes.
  • DIN plug and pigtail came with my IC-7300, I simply cable tied once for strain relief and a second time looping it through two small holes I drilled to stop the cable from rotating. This secured it nicely since I didn't have anything better on hand.
  • Solid state relay is a Crydom DMO063, Mouser part # 558-DMO063. Can also be found on Amazon, and other places.
  • Barrier Terminal Blocks TERMINAL STRIP 6 LUG, Mouser part # 158-1006.
  • RCA Phono Jack, Mouser part # 490-RCJ-032.

Monday, December 16, 2019

Ameritron AL-80B AM Operation


Since I get into a bit of AM on 75 m, I had wondered about using my AL-80B for some extra Amplitude Modulation power :-)

While chatting on 75 m AM today I raised the question about using an AL-80B on AM. A couple of the ops in the round table we had going said they work great, in-fact one who later joined-in was using an AL-80B!

Setting up an AL-80B for AM use is pretty simple, the goal is 100W unmodulated carrier power on AM from the amp.
  • With the Icom IC-7300 set to 30% / 30W on RTTY mode, tuned the amp, this delivered about 400W output.
  • Switching to AM I reduced the drive power (to 20% in my case) to where I got 100W unmodulated carrier power from the amp, modulated voice peaks are around 300W PEP.

With this configuration I found that anode would start to show a dull cherry red color after a few minutes of transmitting which is perfect for the 3-500Z tube.

Signal reports from the group indicated going to 100W carrier power made a worth while improvement over the 25W carrier / 100W PEP from the IC-7300 on AM.

The AM operators in the Pacific North West are a friendly bunch, if you enjoy informal round table QSOs that can last a while, then this is the place (3.870, 3.877 and 3.885 MHz).

Wednesday, November 27, 2019

New Desk version 2

Earlier this year I got some IKEA for the shack, the setup was ok for ham radio use where I might spend an hour or two.

The company I work for offers the luxury of working from home up-to a couple days a week (perk of working in tech) which I've been doing more of recently. I was finding the ergonomics of my IKEA setup not great after 7 or 8 hours of use.

I needed something better. After some searching I came across Cymax Bush Business Furniture, yes it costs a bit more but the quality is good with a 10 year warranty. I got the Bush Business A-Series Left Corner Office Suite in Hansen Cherry, which is just two Series A 36W Desks and a Series A 48W Corner Desk.



Much better!

The Bush Business setup was just over $600 delivered, not cheap but the quality is there. Feels solid and can handle up-to 200 lb / 100 kg, ideal for those heavy vacuum tube amps. They shipped fast too, ordered Saturday delivered Wednesday morning, had it assembled and in-place by the end of the day.

Previous setup:



The three IKEA draw sets are now under the window just out of view on the right in the first pic, these made up most of the cost of the previous setup, the two IKEA table tops were $30 each at the time I got them so no big deal.

Saturday, November 16, 2019

A Better Off Center Fed Dipole?

Experimenting with OCFD models, I discovered adding 175 pF series capacitance at the feed point moved the resonance on 80, 40, 20 and 10 m into the phone (SSB/AM) segments of these bands. I call this an "FPL-OCFD" (Feed Point Loading Network).
  • 80 m - 3.8 MHz, SWR 1.6:1.
    The result falls out of the length and cap value that works best for 40, 20, 10 m.
  • 40 m - 7.2 MHz, SWR 1.33:1.
    Nicely centered across the phone segment.
  • 20 m - 14.275 MHz, SWR 1.3:1.
    Favors upper end where most activity is in North .
  • 10 m - 28.4 MHz, SWR 1.17:1.
    Favors the phone segment of the band where most activity is.

What else can we get out of this? 17 m is close, resonance is just below the band. 12 m looks good. 6 m resonance is just below the band again.
  • 17 m - SWR 2.5:1.
    ATU will take care of that one.
  • 12 m - SWR 1.36:1.
    Bonus!
  • 6 m - 50.0 MHz, SWR is 2.5:1.
    SWR goes up from there. Can't win em all.

Model parameters using EZNEC:
  • 41.3 m wire.
  • 33% offset.
  • 175 pF cap at balun / feed point.
  • 12 m / 40 ft height above ground.
  • 13 AWG, 0.5 mm PVC insulated wire (The Wireman 531 material).

This capacitively loaded OCFD relies on the antenna being physically too long. The capacitive loading network at the balun / feed point has the desired electrical shortening effect, which is greater lower in frequency where it's need more.

My goal was to find something that at a minimum moved 80 m resonance somewhere between 3.7 - 3.9 MHz, and favors phone the segments of 40, 20 and 10 m with low SWR. This satisfies my solid state rig with out needing an ATU, and gives the AL-80B a good match. It's an order better than a conventional OCFD where 80 and 40 m resonance are below the bands, 20 and 10 m end up high in my experience.

I credit the idea of adding capacitance to ON4AA's "CL-OCFD" design which moves the resonance on 80 m (and optionally adds 30 m too). This one locates the capacitor at the center of the antenna, which only affects 80 m and odd harmonic resonance. K5GP's "A broadband 80/160 meter dipole" is another example of using a center loading network.

After a lot of searching, I managed to turn up a couple of references where a capacitor is placed at the balun:

20 m 3D Far Field Plot:
20m 3D Far Field Plot - GAL-ANA

SWR Plots:
80 m SWR 40 m SWR 20 m SWR 17 m SWR 12 m SWR 10 m SWR


The modeling results are a surprise, it was literally a "what if.." thought one morning to place a cap at the balun to see what would happen. I got started building it last weekend, hopefully try it out soon time and weather permitting.

A copy of the MMANA-GAL model I started with, and the EZNEC model can be found at https://www.qsl.net/kl3no/Models/OCFD/

---
This modeling exercise started out in MMANA-GAL which I've been using over the last year to teach my self with. I decided to cross check the results with a demo version of EZNEC.

EZNEC offers a high accuracy ground model (recommended with antennas under 0.2 wave length above ground), and can model the effect of wire insulation. With the ground conductivity configured for my location and insulation defined, I found I had to shorten the antenna model nearly 1 m / 3 ft and increase the value of the capacitor from 150 to 175 pF compared to the MMANA-GAL model.

After spending a few days with EZNEC and the well written manual I decided it was well worth purchasing.
---

Update 01 Dec 2019:

I got the antenna assembled and up semi inverted V, with out the cap for now.

SWR sweep:



As expected resonance is low on 80, 40, 20, 17, 12 m. 15 m unexpectedly is under 3:1, 10 m pretty good.

Update 08 Dec 2019:

The trees between the front and back yard are too close together by about 15 feet for the 90+ ft long leg. The best I could do was run the long leg from the front yard tree to the tree in the back yard, with the balun hanging between the last 15 ft of the long leg and where the short leg is tied off, but the tension needed to get most of the sag out is more than I can supply which causes the short leg to get mixed up in the lower branches of a Maple tree.

Tried to find a solution with EZNEC using a 80 ft / 50 ft or so split, no dice with an offset much other than 33%.. Well, the positioning of my trees sure has let the air out of my tires on this one..

I may be-able to get the antenna situated by bending the end of the long leg down and hanging the balun further out on a limb. That's easier said than done in cold rainy weather with a pair of Maple tress in the way that snag wire anytime it gets near..

For now I have left the capacitor out and shortened things to get 40 m and 20 m to fall into place, still needs a couple more tweaks. This improved 17 m and 15 m, but need ATU to dial them in. 12 m looks good, 10 m is towards the upper end of 28 MHz. 80 / 75 m SWR is 1.5:1 at 3.650 MHz rising to 2:1 at 3.850, and 2.8:1 at 4 MHz. I have a harsh sounding noise level on 80 m up-to S9 at times, the next crusade might be see if it's originating from with-in our house and eliminating it.

Receive wise it works as expected, not had much time for QSOs except some 75 m AM during the day using the IC-7300 barefoot (25 W carrier power / 100 W PEP) with good signal reports.

Update 15 Dec 2019:

After some more trimming:



  • 80 / 75 m centered on 3.750.
  • 40 m centered on 7.000 - SWR rises to just under 2:1 at 7.300.
  • 20 m centered on 14.200 - SWR low across the band.
  • 17 m centered on 18.075 - SWR is under 1.5:1 across band.
  • 15 m SWR 2:1 at bottom, 1.8:1 at top of band.
  • 12 m SWR under 2:1, resonance moved above the band.
  • 10 m SWR good across the band.

I need to trim the short end maybe 10 cm or less to pull 20 and 17 m up a little more, wont make much difference on 40 or 80 m.

In essence I may have wound up with something fairly reasonable with out needing a loading network. 15 m is close enough to be a bonus, and I exchanged a good match on 12 m for 17 m which is more useful during solar minimum. 40 m is a bit low, 10 m sweet spot at 29.3 MHz, but its good enough for a weekly net or two around 28.4 MHz. 80 / 75 m is much higher up the band than expected, the last two OCFD antennas I've had previously would favor the bottom of the band.

Overall I'm pleased with it given the situation.

I still want to explore how the FPL (Feed Point Loading Network) shapes up in practice, maybe next summer.

Thursday, October 17, 2019

WSPR - Turning off MW Band Attenuation for 630m

About three weeks ago I decided to turn off the MW band attenuation in the Icom IC-7300 - this is a sub menu option in the settings that is on by default. Wow what a difference! I started spotting stations much further away from Australia, Hawaii, Alaska, midwest to the east coast.

I've been spotting these stations semi-individually on and off, finally got a good selection of them in one night:
  • VK4YB - Roger's 630m antenna is something else.
  • K9FD - on a former AM broadcast site with radials intact on an Island, dream location!
  • K3MF
  • K5DNL - holds the distance record for a QSO on 630m with VK4YB!
  • KL7L


The antenna I'm using on receive is the ZS6BKW with no additional matching, just an HF 1:1 current choke at the bottom of the ladder line, remote ATU (bypassed) then 10ft coax drop to ground where it runs around to the other side of the house. The other RX settings I configure when running WSPR with the IC-7300 are NB and NR off, notch filter off, AGC fast set to 0.3 seconds.

Since turning off the MW band attenuation, I would start spotting the closer stations in California as soon as it got dark through until sunrise like clockwork. First I thought it was propagation changing with the D layer absorption which quickly disappears at sunset and quickly returns at sunrise.

Turns out it's more than the D layer at work, there are several strong AM broadcast stations in my area, during the daytime they are very strong and overload the receiver in the IC-7300. At night these stations lower output power and/or change their antenna pattern, this reduces signal levels at my location to a level where the receiver can cope.


Screen capture of the strong signal on 850 kHz during daytime, S meter maxed out at +60dB. There are several more at +40 to +50dB.


630m band WSPR frequency during daytime, the S meter hovers around S9 +15dB. Band scope shows the "mess" these strong AM broadcast stations create in the receiver.


630m band WSPR frequency at night, the S meter hovers around S1 when AM broadcast stations reduce power and/or switch their antenna patterns.

Note: The time displayed on the IC-7300 clock top right is UTC.


Update 04 Dec 2019:

Since switching back to using an OCFD a few days ago, I no longer have the receiver overloading issue during the day on 630m. It seems to have knocked back the signal levels from the AM broadcast stations enough but with out appearing to adversely affect the WSPR receive performance.

Saturday, September 21, 2019

Gain vs Wave Angle

Something I've noticed is that most don't consider is the whole picture when it comes to antenna gain. Often only peak gain at the wave angle it occurs at is quoted. Sometimes a pattern is shown with no gain figures which is useless, this is often the case with verticals.

To build a picture of what one might expect when considering low band DX antennas, I feel it's better to consider the gain at different wave angles.

To illustrate this, I created a table in a spreadsheet with several different antennas and the gain they have at different angles. LiberOffice Calc has the option to fill cell background color based on the value. The table is sorted based on the gain at 5 degrees.



I used MMANA-GAL for the modeling of these antennas. Most are 40m antennas, those that can be matched on 80m are also shown.

Wire antenna heights are 40ft/12m, the inverted Vs are 15m/50ft, the delta loops have a minimum height of 1m/3ft.

Nov 15 2019:
Looking at the models of OCFDs again - I realized due to the lobe formation being either side of the X or Y axis on 40m and above, the far field plot does not show the peak gain as its simply sliced down the X axis. The geometry would need to be offset such that one of the main lobes aligns with the X axis. Comparing the elevation and gain results on the calculation tab with a plain 40m dipole vs an 80m OCFD on 40m band, the OCFD has around 1 dBi more gain at the same elevation angle (52 degrees when 12m above ground), which comes from the two broadside nulls that form. Under far field plots, the far field elevation angle can be changed, comparing gain at 40, 30, 20 and 10 degrees shows the OCFD having about 1 dBi more than a dipole at the same height.

I'll need to update my table..

Monday, September 9, 2019

ZS6BKW Antenna

One of the antenna projects I wanted to get finished off this summer was get the 40m OCFD up in a flat-top configuration.

Got thinking about how I'd lack an antenna that covers 75m NVIS, thought about an 80m OCFD again. At 135ft long, the current situation with tree shapes, sizes and locations leave that easier said than done, and not for a lack of trying with out resorting to chainsaws. Having said that, getting one of two 80ft Fir trees closest to the house removed is on the list, so I may be-able put up longer wire antennas in the future.

What else is there that's under 100ft, at a minimum covers 40 and 20m with out the need for an ATU, and will work on 75m?

After considering a few ideas, I took a closer look at the ZS6BKW antenna which is an optimized variant of the well known G5RV. This antenna checks the boxes on these points:
  • Light weight - no traps, coax etc hanging.
  • Low SWR on 40 and 20m, can run ~1kW with the AL-80B.
  • Respectable gain on 20m if you have the luck or luxury of orientating the broadside to favor somewhere of interest.
  • Will work on 75m with the remote ATU I already have. It's essentially a 1/3 wave dipole, as such has reduced efficiency since the resistive component falls rapidly when a dipole is under 3/8 wave length.
  • Also covers 17, 12, part 10 and 6m with low SWR. 17m opens occasionally during the current solar minimum, and there is the Puget Sound 10m net on Sunday nights I like to take part in.

Spent a couple weeks reading everything I could find, and playing with models - one is included with MMANA-GAL, others can be found online.

Decided it was worth trying out. Initially I was going to order the parts from The Wireman and build it my self, but found a source of these pre-made cheaper and better built for $60 (normally $90) plus shipping from Amateur Radio Supplies => ZS6BKW G5RV 80, so went that route. 

Current setup:
  • Antenna apex at 50ft, ends in inverted V configuration.
  • K9YC inspired choke balun - 7 turns of RG-8X through two mix 31 clamp on ferrites.
  • Remote ATU between the choke and coax to the shack. 

How does it work?
  • Except for 15m, low SWR on six bands from 40 to 12m, parts of 10 and 6m.
  • Remote ATU dials it in on 75, 60, and 15m, brings the total to nine bands.
  • 30m is the odd one out, ATU fails to find a match in my case.

Nine bands where only three need an ATU, with 93 feet of wire in the air is OK by me. 30m might be an issue for some, but you can't always win 'em all :-) 

Links to further information:

Monday, August 12, 2019

Bay of Islands ARC Repeater Site

Following on from the Auckland VHF Group Repeater Site post, some more pics from the archives. This time of the Bay of Islands ARC Repeater Site, photos I took from around 2007 when I had the task of reinstalling the equipment after it had been removed for re-alignment.

This site was established with the help of the Auckland VHF Group in the mid 90s to get the national link extended north via a sister site between here and Auckland called Brynderwyn. NZART map here - its approximate at best. Google Map that I created here, the locations are with-in tens of feet in most cases.

Since these photos were taken when I was last there, the 2m repeater has had some changes with the addition of CTCSS for IRLP node 6398 link, there are more recent pics on their homepage and some from when the tower was erected.


Pic of the tower and antennas. Like Klondyke, the 2m repeater antenna is constructed from angle iron, welded, and hot dip galvanized, but is a simple pair of 2 half waves in phase for around 10 dBi of gain, hard to see as they are end on in this pic. At the top is a 4 dipole stack for the the 70cm repeater. This configuration resulted in the 2m and 70cm repeater performance and coverage being closely matched in most cases. The link to Brynderwyn is a set of four 7 element Yagis with around 17 dBi? of gain, the Brynderwyn end has the same antenna configuration, this is needed because the 70 mile path is not ideal.


Inside the building.
Tait T300 gear.
146.750- also had a 50W PA in the back.
439.975- had the matching Tait 50W PA.

Thursday, July 4, 2019

New Desk

After using a folding table for the last few months, 'twas time for a something better.

I had considered The Great Ham Radio Desk Project, but after looking around IKEA I found something I liked better, more so since IKEA was having a sale at the time.

The spare room/office/shack is 120" wide across the back wall. What I ended up getting were three sets of draws and two table tops, the table tops are 59" x 29", the 29" width is nice, as it allows plenty of depth for radios, computers etc with space in-font.


The total was about $270 less tax and delivery fee, took an afternoon to put together.



Left to right, Ameritron AL-80B, Kenwood TH-D72A HT on top, Motorola MCS 2000 33cm/900MHz radio, Kenwood TM-731A, Icom IC-7300, 27" iMac (2014, 5K), under the iMac is a Windows 7 laptop which runs all the ham radio applications.

Plenty of room for more stuff! Plan to add some shelves to mount the Kenwood and Motorola mobile rigs, control boxes, and antenna switches etc.

22 Nov 2019:

This arrangement has been superseded with New Desk version 2.

Saturday, May 25, 2019

40m OCFD

After previously re-considering verticals or dipoles, I decided to build an OCFD using ON4AA's design and ordered a Model 4116 balun from Balun Designs LLC.

To start with, I have decided to keep things simple by comparing verticals and dipoles on 40 m. I could put up a simple 40 m dipole, but had this balun already.

Looking at 40 m OCFD designs, none seemed to be that great. SWR over 2:1 on 40 m, or different offsets to get 15 m resulting in worse matches on other bands.

Having recently acquired a used Ameritron AL-80B from VA7ST, I also now need an antenna with a good match on 40 and 20 m that will take some power - up-to 1 kW PEP. My LDG remote ATU is rated to 600W PEP, at high(er) power levels I'd prefer to have properly matched antennas available.

I also bought An Introduction to Antenna Modeling with my $10 birthday coupon from the ARRL, this has good info for getting started with antenna modeling. With some ideas in mind from the book and what ON4AA described with their 80 m center loaded OCFD design, I set a design goal of a good match (under 1.8:1) on 40 and 20 m..

The process I followed:
  1. MMANA-GAL, using real ground, and a height of 12 m / 39 ft (my situation).
  2. I started by finding the resonant length for a 20 m dipole at 14.2 MHz = 10.45 m.
  3. Double the length to 20.9 m.
  4. Tried various offsets between 17% and 40%.
  5. Found 33% is the best compromise between 40 and 20 m.
  6. An added bonus is low SWR on 28.5 MHz and 50.1 MHz.

Results:

07.15 MHz, R 144, jX 74.6, SWR 1.72, Ga dBi 5.58, Elev 51.1
14.20 MHz, R 122, jX 2.39, SWR 1.64, Ga dBi 8.12, Elev 24.5
28.50 MHz, R 162, jX 14.8, SWR 1.25, Ga dBi 9.44, Elev 12.3
50.10 MHz, R 202, jX 32.1, SWR 1.17, Ga dBi 11.2, Elev 7.00

I have rounded the numbers above slightly for better formatting. Now, time for some pretty charts:

40 m
20 m
10 m
6 m



Next step, build it and see!

Notes:
  • The averaged R across the four bands is 157 ohms, using a 3:1 balun would get [in theory since this is a model after all!] an improved match.
  • On 40 m, resonance is just below the band. Borrowing from ON4AA's center loaded design using a capacitor in the center to resonate the antenna on the lowest band, 425 pF did the trick in the model.
  • Moving the feed-point to 40% enables 15 m, but results in higher SWR on 40 and 6 m bands.

Model files for conventional 33% offset, center loaded, and 40% offset can be found here: https://qsl.net/kl3no/Models/OCFD/

Saturday, April 27, 2019

WSPR - 40m, ZL5A Scott Base Antarctica

WSPR pulls out another surprise.

Adam Campbell / ZL5A from Scott Base Antartica:




Saturday, April 13, 2019

The 900MHz Club

After getting to know a new group in my area on the local N7OEP 70cm/6m linked system, there is occasional chatter about "the 900MHz club". Otherwise known as the 33 centimeter band.

ZL has an allocation from 921 to 928MHz, commercial two way radio gear is non existent that I know of except for the digital Tetra system around 860MHz. If there was analogue FM stuff around to modify, the commercial 25MHz repeater splits are too wide for the band. As far as I know, there is no activity on this band in ZL bar maybe a mad scientist or two frankensteining something together in their basement shacks. Those into things above 70cm start at 1296MHz and up into the microwave bands from there.

The US has 902 to 928MHz allocated, and here in Western Washington we have several 900MHz repeaters and some activity. Getting on 900MHz requires sourcing, reprogramming and sometimes making physical modifications to commercial 900MHz two-way radios.

I ordered two Motorola MCS 2000s from Used Radios, they shipped quickly, were well packaged and the two I got appear to be in good condition. The pair I got are the version 3 model that also make 35 Watts, 35 Watts at near microwave frequencies is rather respectable. Here in the Puget Sound area there are a couple of people happy to program the Motorola rigs. As for antenna's plenty of cellular stuff around that covers this band, cheap Yagi's can be found on e-bay and Amazon, or in the spirit of ham radio, make something! I ordered a couple 7 element 900MHz Yagis to try out at $16 each.

 

See Getting Started with 900Mhz (33cm) Ham Band by WA6AER for more info about whats what. The largest hurdle with this stuff is getting the radios programmed, either your self or by someone else.

Whats it like? Well like FM anywhere else except using a commercial Motorola radio gives things an industrial feel, no S meter, basic controls - on/off, volume, memory up/down, and a bunch of buttons that do nothing.



Time for something bigger and better than a folding table.

Tuesday, March 19, 2019

WSPR - 40m, 1 Watt, 16441 km

Distance wise, this is the 2nd best spot I've reported yet at 16441 km / 10216 mi, from ZS1LCD in Cape Town South Africa who was running 1 watt on 40m [7MHz]. ZS1OA remains king at 16511 km / 10259 mi on 30m [10MHz], and ZS3D is a regular in 3rd place at 16233 km / 10087 mi on 40m.


After running WSPR for about three months, I took a break from it about a week ago having built up a good feel for what I can expect with the current antenna configuration. Last night I had it running again after adding a 20 ft horizontal wire to the top of the 43 ft vertical turning it into a 1/4 wave inverted L on 80m.

With the exception of 60m, Remote ATU has no problem finding 1:1 match 80 thru 10m, 40m was the surprise since the antenna is close to a 1/2 wave. Hard to know with out an antenna analyzer to see what is really going on. I'll soon have a better idea, ordered a RigExpert AA-55 analyzer, and another 40 x 32 ft radials for the vertical / inverted L to bring the total to 60.

Monday, March 18, 2019

Extra Class

This past Saturday I made the trip to Renton where the Mike and Key club run VE testing sessions.

It took about 4 months of study and the practice exams on QRZ to reach an average score of 80%. To pass you need a score of 74%, out of 50 questions you can get 13 wrong.

The good news is I passed!

I think the incentive based system here is a good way to manage access to HF bands, in addition to creating an incentive to further your skill and knowledge, regardless of how "irrelevant" some think the subject matter and questions are.

Wednesday, January 23, 2019

Auckland VHF Group Repeater Site

I recently ran across some photos of the primary Auckland VHF Group repeater site someone had sent me, I don't recall who. However, repeater systems are a subject that interests me, so I tend to absorb details and turn inside-out with excitement when someone offers to take me along for a site visit.


The Auckland VHF Group is located in Auckland New Zealand. Along with the Waikato VHF Group, and the Wellington VHF Group, these clubs have strong membership and skill levels. A subset of members have day jobs in RF engineering and radio communication fields. These three clubs built some great repeater systems in their respective areas.

They would also outreach into other areas and help clubs get well engineered repeater systems up and running. Most of this work was done in the mid '80s, during what was arguably the heyday of ham radio clubs when memberships peaked.

Getting back to the Auckland VHF Group, they built a repeater site named Klondyke after the road it's on. Located at Port Waikato on the west coast, it's about 40 miles south west of Auckland city.

This site served as the Auckland end of the 70cm [430MHz] national link when first built which linked to Wellington [Belmont 439.875-] about 300 miles south via one intermediate site located on Mt Taranaki [Egmont 434.900+]. Over the years it has since expanded to dozens of linked repeaters, exclusively RF linked on 70cm - NZART map here - its approximate at best. Google Map that I created here, the locations are with-in tens of feet in most cases.

With that out of the way, the point of this post is more the 2m repeater at the site. 146.625- a.k.a. "Auckland 6625", my knowledge of the equipment used is somewhat vague, but this is from what I recall of conversations I had around 10 years ago with Colin ZL1ACM who was one of the principal engineers of the site. The repeater hardware is [or was] Tait T300 gear, with two voted receivers, two exciters, two sets of duplexers, and two power amplifiers set to about 40W - This balanced the TX and RX range with typical 25W to 50W 2m mobile rigs, no one likes a repeater that talks further than it hears!.. Nothing too amazing there compared to some of the ham radio repeater systems built in the US..

Now, onto the fun part. The antenna system they built I think is an amazing feat of engineering for a ham radio club!

These are broad side collinear arrays, but rather than have resonant reflectors, they have a grid type panel behind the driven elements. The antennas were constructed from steel, the driven element stand offs [The center of a 1/2 wave dipole can be grounded with no ill effects] and dipoles are angle iron, everything - reflector panel, stand offs, and driven elements - are welded and hot dip galvanized as one piece.

There is a north bay, and a south bay [hence the two sets of receive and transmit chains], each panel has three sets of two half wave dipoles fed in phase, there are four of these panels stacked on each side. This adds up to around 18dBi of gain per side?! The beam width is 70 degrees from memory.

Above is a shot of the tower and building, HF wire antenna can be made out, this is used to transmit the monthly NZART official broadcast on 3.900MHz, as well as out on the 2m repeater and 70cm national link system.


Here is a close up with some details marked out, each of the four bays on each side is fed in at the middle set of dipoles, you can make out the crossed phasing lines.

You can also see someone climbing the tower, they moved the 70cm link yagi to Mt Taranaki [Egmont 434.900+] further up the tower as there were some pine trees near by growing up and obstructing the path

These photos are from 2009.

One of the really interesting things about this 2m repeater and its astronomical antenna gain, it is very very very sensitive to band conditions once you got around 100 plus miles away. If there was the slightest hint of a band lift, this repeater would shoot up the S meter in strength. Once it pegged at S9+30dB, it was time to start looking for band openings. Some times it would consistently swing in signal level from seconds to minutes, other times it would bottom out and disappear all together..

This repeater could be reliably worked up-to 150 miles in each direction, with the potential for 300 mile separation between stations at the opposite ends of its coverage. Much of this is over less than ideal paths, not bad considering the repeater site is only 1309ft ASL. When band lifts are present the range would easily extend beyond this.

Now some say this antenna design was borrowed from the Mt Kaukau VHF low band [45MHz and 55MHz] TV broadcast antennas, click the image below for a high res version, and look at the top, horizontally polarized for TV, but looks familiar doesn't it? The Belmont 147.100+ repeater built by the Wellington VHF Group also used antennas based on this design.




Saturday, January 19, 2019

19" Radials on the Diamond X50

After reading Runt Radials I ordered some 19" radials from Comet, these also fit the Diamond antennas.

My Diamond X50 came with the 7" radials, and I've had problems with the coax getting "hot" [common mode currents] with RF when using it on 2m.

Here's what the 19" radials look like



Diamond X50 mounted on 2nd level deck. I'm located in the south Puget Sound at 400ft ASL, and have a clear view north towards Seattle (35 miles north), this is a secondary antenna connected to my Kenwood TH-D72 hand held. With 500 mW I can open the 145.190MHz N7GDE repeater located 100 miles north of my location.

While I have not done any form of testing that's scientific, the anecdotal results are slightly better performance on both 2m and 70cm, with the added bonus of the feedline being better decoupled from the antenna on 2m.

Sunday, January 13, 2019

CHIRP, Kenwood TH-D72 and WWARA DB Extract

How to use the WWARA coordinated repeater DB extract, Excel or LibreOffice Calc, and CHIRP to program a Kenwood TH-D72 - or any other CHRIP supported rig. Noting this to remind my self how to do it in 17 easy steps!

  • CHIRP - Free programming software
  • WWARA > CSV Database Extract [includes CHIRP formatted file] 
  • LibreOffice - Calc / Spreadsheet - used to edit the CSV file [CHIRP sucks at this]
The Process:
  1. Create backup of the rig to be programmed, in my case I use Kenwood's MCP-4A application.
  2. Download and unzip the Database Extract from WWARA.
  3. Open the CHIRP formatted file in CHRIP, and export it as a CSV file.
  4. Open the CHIRP formatted CSV file in Calc or Excel.
  5. Delete the rows you don't want. In my case I remove the 6m, 220MHz, everything above 70cm, and anything that is not an analogue FM repeater - for that I use the custom column sorting to group repeaters marked as digital together for deletion, and column sort Location numbers again when done to get whats left back in order.
  6. Optional, the Location column numbering can be fixed using the fill down function to sequentially number the memories we are keeping.
  7. I add in my custom APRS, IRLP nodes, and other things starting around memory location 980. The Location column can skip unused memory locations out, e.g. mine jumps from 266 to 980.
  8. Save it as a CSV file again and close Calc / Excel.
  9. Open CHIRP.
  10. Connect the radio to be programmed.
  11. Perform a read/download, and save it as backup.
  12. Open the edited CSV file.
  13. Eyeball it to make sure nothing is out of place, if so, close CHIRP and fix the CSV file.
  14. Clear/delete everything from the tab containing the information from the read/download, copy and paste from the CSV file tab. The exact steps to do this have changed at least once between CHIRP versions.
  15. Write the config back to the radio.
  16. Done!
  17. Not so fast, I then read the config in the Kenwood MCP-4A application again, and save it as a backup.

Saturday, January 12, 2019

Comet GP-15 and 6 Meters

The Comet GP-15 is a single piece tri-band antenna that covers 6m, 2m and 70cm.

The 6m band is "tuned in" via loaded [1/4 wave on 6m] radial that is adjustable with about 1MHz of bandwidth, the other two supplied radials are 1/4 wave on 2m, and double as 3/4 wave radials on 70cm, which is fine for these two bands. The GP-15 is phased as a single 5/8 on 6m, but the single radial lets it down..

Issues with this configuration, the single 6m radial results in narrow bandwidth, and more importantly, may not properly decouple the antenna from the feed-line! Take a look at:
  • Runt radials - This talks about the Diamond X50 and Comet GP-3 with 7" radials [1/4 wave on 70cm] which do nothing on 2m [1/3 of the frequency]. Same theory, since the two 19" radials [1/4 wave on 2m] on the GP-15 do nothing on 6m [1/3 of the frequency].
  • Modifications to the Diamond V2000 and similar antennas - This reveals the Diamond V2000 is less than ideal on 6m. Diamond call it a 1/2 wave, which is technically correct, but its more like 1/4 wave with one radial, that performs less than ideally.
  • EA4EOZ also did a V2000 teardown, interesting to see what's inside these things.
  • Experimenting With 6 Meter Ground Plane Antennas - If these guys have a problem with the single radial on 6m, then it's worth paying some attention to.
Since learning about the compromise radials on these antennas, I decided to try out a set of three full sized 1/4 radials for 6m, the comparison:

First with the supplied tuning radial centered around the FM repeater inputs used in Western Washington:

SWR plot on an Icom IC-7300, 50.0 - 54.0 MHz [500KHz steps]. With the supplied tuning radial, the bandwidth is 2MHz at most.

Quite narrow banded! SWR starts to get high at the bottom end of the band with the North American SSB call freq at 50.125. SWR starts to get high again at the upper end of the FM repeater inputs.

Next up, three full sized 1/4 wave radials, I trimmed these until the SWR just started to sneak up from 1:1 at 50.0 MHz:

SWR plot on an Icom IC-7300, 50.0 - 54.0 MHz [500KHz steps]. With three full sized 1/4 wave radials, bandwidth is 3MHz or more.

Very nice, the bandwidth is nearly doubled! The antenna is now usable down to 50.0, and up into the FM repeater inputs in my area. I'm thinking I could cover the top 2MHz of the band with a second set of radials cut shorter and placed in-between the longer ones.


The 6m 1/4 wave radials I made out of some wire, with lugs crimped, soldered, applied "Lanocote", some heat shrink to seal it in, and offer strain relief where the wire is crimped. I attached them between the locking nuts and antenna base where the radials screw in, applied more "Lanocote" for good measure. The antenna is on a short TV J-Mount on an roof apex, two of the wire radials are laid on the roof which slopes away - note my roof is composite shingle over plywood and not tin/metal as is more common in other countries - the other has a short section of thin nylon rope to hold it up at about the same angle.

I replaced the 6m "tuning" radial with a regular radial like the other two supplied radials - I ordered this directly from Comet, along with three more 19" radials for my X50, total cost with postage $36, and yes they use the same thread and locking nut sizes!

The EA4OEZ V2000 mod replaces the factory radials with an M6 bolt and aluminum tubing.

As for the 19" radials, it's not clear where to get these radials from, no one lists them as something you can buy, not knowing where to start, I emailed HRO, Diamond, and Comet asking if they sold these. Comet quickly replied.

Thursday, January 10, 2019

Remote Operating with CommCat

One thing that caught my interest some time ago was the ability to remote control your station, in earlier times this wasn't so easy, but was possible by interconnecting various different pieces of tech together.

This usually consisted of among other things, computer rig control - building the control and audio interface cables, software - HRD for control, Skype on auto answer for the audio, and something like LogMeIn to gain remote access to the PC in the shack that ties it all together, and a laptop with wifi or cellular connection. A friend of mine, ZL1TLJ [SK], was doing exactly that type of setup with a Yaesu FT-1000MP Mark-V Field around 15 years ago.

Much to my delight, things are a little easier now!

The Icom IC-7300 I have offers a USB port that presents to the computer a virtual RS-232 COM port for control, and USB audio devices for audio in and out. One cable does it all, modern rigs are finally in the 21st century!

I figured that by now someone would have written a remote control app for smart phones, turns out one person did with the generosity to make basic functionality free.

See CommCat and CommCat Live - for the applications, documentation - very well written - easy to read, follow and learn from.

Whats needed:
  • A Windows computer connected to the rig is still required to "interface" via.
  • The iOS app [the client] CommCat Mobile is free from the App Store.
  • The Windows application [the server] CommCat QSXer, is what CommCat Mobile talks to, is free to download, and simple to configure.
  • Audio - a small yearly subscription is required to enable it in the CommCat apps, or you can configure an alternate Skype account to auto answer [remember to lock down the settings so only YOU can call it!].
  • The TCP/IP communication via the iOS client app and the Windows server app [which controls the rig] is direct, there is no cloud service in the middle to broker the connection.
    • Ever wonder how your smart phone apps - from anywhere - can find and control smart home devices in your home for example? Yes magic in the middle makes it happen.
  • For this you need to either forward a port in your router [and be aware anyone on the internet can find this port and try and attempt to interact with it], or run a VPN service from your home internet - this is what I do as I run pfSense as my firewall with my cable modem in bridged mode.
With this setup, I can do basic remote control of my rig, which is all I wanted for now. With this I can tune around the bands, change modes, swap between VFO and memory, setup preset user-defined macros in CommCat Mobile to perform other supported functions.

Downsides? A few:
  • Even with CI-V transceive turned off in the Icom IC-7300, the iOS app will toggle split mode on and off several times after tuning frequencies - somewhat annoying, as you have to wait for this toggling to finish before you can do anything else.
  • 60m band not channelized - fixed by setting up macros - this involved learning the Icom CI-V commands [well documented], and trial and error to get them right.
  • No AM mode - fixed by setting a macro.
  • No 5 or 25 Kc steps.
  • No ability to switch the rig to memory mode and step through preset memories - I can likely work around this will more macros, but not figured them out yet!
  • Skype on iOS seems to eat batteries, even just receiving an audio stream with the screen off! I'll assume that getting the audio enabled in the CommCat apps is more efficient.
  • Mute the mic in Skype on iOS when just listening, otherwise the feedback cancelling will mute the incoming audio when local noise / bumping the mic happens. 

There you have it, this works, costs nothing for basic functions, and after getting the audio levels right, I have held conversations while remote on a local 6m FM repeater with good audio reports using the Apple supplied earbuds/mic that came with my iPhone 6.