6m/70cm antenna updates at the QTH

I have made some changes to my antenna set up. A local amateur was selling a second 13-element 70cm yagi and a 6m HB9CV antenna at a low price so decided to acquire them.

The 70cm yagi was to replace the small 7-element one which I pressed into service as a hand held antenna for potentially finding my HAB payloads last year.

To be honest I wasn’t really after a 6m antenna due to the size and visual impact. I have a 6m ‘wooden’ moxon I made back in 2014 but it is heavy, ugly and unstable so had been collecting cobwebs in the garage. I decided with the prospect of ‘Sporadic E’ season around the corner I would be foolish not to put it up.

The HB9CV wasn’t in the best of conditions but seemed complete albeit it was purchased dismantled. The elements were a little weathered so I set about cleaning them up with a light rubbing down with some wire wool and a rag with a drop of WD40. On closer inspection the tube that made up the front element had some noticeable bending and on removing the plastic mounting to investigate I spotted a crack in the tube wall by the hole for the mounting bolt.

While it hadn’t totally separated it would only be a matter of time before it did fail as it was flexing, the plastic mount was the only thing holding it together. I found a suitable piece of alloy tube from a scrap antenna which was a perfect fit inside the broken element. I cut a suitable length and pushed it up inside the element to the appropriate position and then simply drilled through and bolted either side of the central hole to stabilise and strengthen it (can be seen in image below)

The next issue I had to address was the feed point, it came with about six inches of RG58 coax projecting from it where it had simply been cut for removal by the previous owner. I prised off the cover cap to find it full of water, the reason being a hole in the back and it being stored outside I believe.

Thankfully the trimming capacitor seemed okay, while it was wet it wasn’t corroded. It was all dried out and the hole plugged with silicon and I set about re-assembling the antenna which was a little fiddly to get the phasing line to sit properly but once done it was a simple matter of adjusting the capacitor to get the VSWR to a minimum in the SSB section of the 6m band. I mounted on the rotator pole just below the X50 collinear.

I used it last month in the 6m UKAC and while my operating not exactly earth shattering I was happy with its performance using just 10W in the low power section just “search and pouncing” for a little over an hour.
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The 70cm Yagi was straight forward as was already assembled, I just had to make a slight tweak to the gamma-matching bar as the VSWR was unexpectedly high around 2:1 in the SSB segment of the band, it seemed to have been tuned for the FM portion of the band. I managed just an hour “search and pouncing” in Aprils 70cm UKAC, I started late and while signal reports both ways were a marked improvement I found the extra directionality and off beam rejection something I will have to get used not helped by a temperamental rotator. 

Some reception reports

Not much to report, but have had a few decent monitoring sessions with the FUNCube Dongle.

A couple of ISS ARISS School Contacts took place over Europe during the last couple of weeks, with another taking place on Sunday morning. I was in work during the passes but managed to remotely log in to my computer to do some ‘unattended’ SDR-Radio recordings.

ARISS School Contact 31-Aug-2012 by nerdsville

ARISS School Contact 07-Sep-2012 by nerdsville

Late last night there was a bit of a lift on VHF and managed to receive the GB3VHF 144MHz Beacon which while it may not seem very news worthy is given there is a huge hill in the way when you look towards Kent! I have received it before using the Yagi in an horizontal polarization. But last nights reception was via the discone in the loft, which was a first. Love the JT65B tones, very musical.

GB3VHF by nerdsville

Earlier last night was also quite amusing when I stumbled across the Hucknall Rolls-Royce Amateur Radio Club who were trying to run an Amateur Radio Direction Finding Fox-hunt but were being completely blotted out by another, seemingly deaf, local operator pumping out 100W, though he did turn it down to 10W eventually.

Amateur Radio Direction Finding – Or Not! by nerdsville

Finally last weekend was the RSGB 144MHz Trophy Contest, again I got to get some decent SSB reception.

144MHz Trophy Contest – Part 1 by nerdsville

144MHz Trophy Contest – Part 2 by nerdsville

Some audio from the 144MHz SSB Contest

Not had much radio time since Saturday due to family duties but did managed to find time to edit down some of the audio from the 144MHz SSB Amateur Radio Contest I received.

The first part of the audio was from the FUNCube Dongle, the latter part from the Ultra cheap NewSky DVB-T stick running the RTL-SDR driver.

Both were received using the loft mounted discone antenna which I believe is vertically polarised and so wasn’t optimal since SSB is broadcast using horizontal polarization. Even so I was quite impressed with what I did receive with such humble equipment.The stations calling in the audio were G0VHF (morse and voice), M0KWP, M0BAA, 2E0KWM and G4SIV

  144MHZ SSB Contest by nerdsville

Please note the corruption that can be heard toward the end of audio appears to be an artifact of the sound editor and/or the transcoding used by soundcloud as it wasn’t in the original audio.

RTLSDR – Part 3 – CQ CQ Contest

As it’s the weekend I have managed to experiment with my new SDR device. I have sorted out an adapter so I can connect it to the loft discone and it has been pulling in some very nice clear signals. I have had to do some tweaking especially of the usb transfer buffer size to get some decent audio out of it. I have also had to learn how to use the HDSDR program which I haven’t used much before favouring the SDR-Radio one with the FUNCube Dongle.

One thing that caught me out is that when I last used HDSDR with the FUNCube I had to swap the I and Q signals and I don’t need to with the Newsky Tv28t so initially I was very confused as it all seem arse about face! Duh! But now actually growing to quite like it as having a much wider spectrum to see is very nice.

By a pleasant coincidence yesterday saw the start of the RSGB 144MHz May Contest so lots of SSB transmissions to tune in to. The FUNCube definitely has the edge when it comes to quality of audio and sensitivity and being able to tune down the gain helps in preventing out of band signal overloading the front end. With the Newsky device I’ve had to have the gain right up most of the time, but I suspect there is still more optimising to do.

Just a small video showing some of the SSB Contest signals on the spectrum. Don’t you just love the masses of noise? Really must do something about that damn router!


I’ve also got to discover how to calibrate the Newsky as it shows quite a bit off frequency, I understand I need to discover the actual crystal clock frequency and can feed that into the EXT-IO plugin.

ARISSat-1 Morse beacon

This weekend there are a couple of excellent daytime flybys of ARISSat-1 predicted, passing very high in the sky.  Up till now I have been concentrating on the FM transmission on 145.950MHz which carries the voice messages, voice telemetry and the SSTV. The other signals from the satellite use SSB and CW modulation.

So this morning I left the loft discone and my Realistic PRO2006 with MMSSTV in the spare bedroom waiting for the pass while I took the borrowed Alinco DJ-X10, which has SSB capability, outside and using the Yagi antenna I built up last weekend had a go at getting some of the CW beacon on 145.919MHz

I got a decent signal as you can hear below, and using CWGet managed to decode some of the telemetry and the identification, but the high noise and doppler effect did cause some problems.

Arissat1 cw beacon by nerdsville

While I was doing this the SSTV system caught a lovely image

Can not wait till tomorrow for two almost overhead passes in the morning and then time to watch the Grand Prix!