VK5GR Amateur Radio Adventures

After 7.5hrs in the field today and a further 6 hours building mark 2 of the matching network I am pleased to report that we have successfully provided some modifications to the 80m antenna to transform it into a 160m inverted L. While only 12m high, with a tuned radial plus resonant loading wire we have achieved successful daylight QSOs to several stations. I acknowledge that it isnt very efficient, but it is better than no 160m antenna at all (and hopefully will be a little more effective than the dipole I took to Niue last year).

Steve VK5SFA helped immensely with the tuning and setup today, including loaning me the high voltage capacitors needed for the matching circuit. The 160m design is based partly on those published by DJ0IP showing how to build low band antennas on a 12m Spiderbeam pole.

The 80m design is a scaled up version of one of Steve VK5SFA’s 40m designs that I used on Niue last year. One of the big differences was that it needed the large shunt L coil you see the raise the impedence up to 50ohms to match the radio.

We then took the shunt L out of circuit and added some series C and a top hat wire to form the inverted L for 160m. To tune the 160m antenna, we started with a variable vacuum capacitor to find the correct C value, and then using Steve’s VK5JST Analyser, we  then substituted the variable capacitor with some fixed ones that matched the required 350pf. We then tested the VSWR and were getting around 1.7:1 as our best result at the antenna terminals. Back at the radio, this was represented as better than 1.3:1 which was very good indeed.

Feeling like we had a working antenna, we then called Tony VK5TT and arranged for some on air tests. Tony is on the other side of the Main Mt Lofty range. He was reporting us at 5×9 over a daylight path. We then proceeded to do various trials with tuned radials as well as with adjusting the tuning of the top hat wire. We finally settled on a combination that certainly seemed to be working. Neil VK5KA also joined in the conversation on 160m and we had a very pleasant hour or so tuning and fiddling, while marveling at the fact it worked at all <smile>.

We then put it into 80m mode (bypassing the capacitors and reintroducing the coil) and had similarly successful contacts and then proceeded to tune it up the bands. On 40m it is a full height resonant 40m 1/2 vertical and we were getting 59 and 59+20 reports into VK3. We then verified that it would resonate at 30 and 20m as well before calling it a day, satisfied that apart from finalising some packaging we had a fully verified antenna package ready to take to Vanuatu!

Again – a huge thanks to Steve VK5SFA for all the effort and time he has put in to helping me get this antenna running. Also thanks to Tony VK5TT and Neil VK5KA for their on air testing this afternoon!

See you on 160m FT8 (mostly) from YJ0AG de Grant VK5GR – 2 weeks to go!

 

UPDATE: YJ0AG planned use of expedition mode cancelled awaiting GA release of 1.9.0

Following the explicit requests of Joe K1JT and the development team, and respecting the fact that the code is still in beta, the planned operations for YJ0AG using FT8’s experimental Expedition mode will not go ahead (unless the GA release occurs in time for the expedition in 2 weeks time – not expected).

YJ0AG FT8 Standard Mode Operation Plan

It is my intention however  to still run FT8  on Vanuatu during the activation. On 80m it is likely to be the primary mode used. Depending on traffic I will operate initially on the standard frequencies of 1840, 3573, 7074, 10136, 14074, 18100, 21074, 24915, 28074. From time to time I will potentially also QSY to stand alone frequencies for people to work YJ0AG to avoid causing excess congestion on the main FT8 channels only using the modes currently available in the 1.8.0 version of the software (ie standard FT8 protocol but non standard operating frequencies). See the frequency list down the bottom of the page for alternates.

If I can activate 160m I will operate using either 1840kHz simplex or I will call as ‘YJ0AG QSX1908’ indicating that I am running split frequency operation and am principally looking for Japan.

What is a Valid and Logable QSO?

I have indicated below how far you need to get before I consider your QSO to be in the log. Please take a minute to familiarize yourself with this so that we can have a smooth QSO on FT8. Note I will always operate split mode and will typically call from above 2000Hz on the waterfall. If I don’t see you reply to my reply at +15 seconds (see below) I will give 2 more calls and then move on. This is to maximise the chance of a QSO while being fair to others waiting in the queue.

Broken FT8 Calls will ONLY be processed after the expedition has closed and I return to Australia. Please do not ask my QSL manager to adjudicate broken FT8 calls – I will do that personally!

Further, broken calls in the log will only be resolved by you providing your ALL.TXT file sample via Email to vk5gr@wia.org.au and it being able to be matched to the expedition station ALL.TXT file. Only if the details in the master log on both ends of the contact match will the QSO be considered valid.

Alternate YJ0AG FT8 (standard mode) Frequencies

These have been chosen noting current activity and where possible have attempted to comply at least with the Region 3 band plans, although they should be acceptable for most regions and hopefully have avoided most of the PSK, Olivia, MFSK, Hellshreiber, Mailbox and other activity you see around the digital mode segments of the bands. 80m in particular was chosen to support JA stations (who cant operate above 3575kHz) while remaining above the bottom edge of the 80m band plan.

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A lot of work has been going on in the background building the antenna system that I will take to Vanuatu this year. That work culminated in a first successful on air test this weekend on 80 and 40m. This is a positive development and confirms that 80m will be one of the active bands from Vanuatu next month! I huge thank you must go to Steve VK5SFA who has helped with the design and field validation work and also to Paul VK5SL for his insights as well.

Antenna Design

The antenna is based on the 40m folded monopole solution that was used last year on Niue, but scaled up to 80m. Mechanically it is now based on a 12m Spiderbeam. The design allows for the main radial to be variable in length as well as the ground radials, such that the whole antenna is effectively tune-able from 80m-10m). The design has been modeled in 4NEC2. The results are shown below for 80m.

Structural Details

The design is based on the following basic components:

• 2x Fly Fishing Reels
• 1x Nylon cutting board
• 1x 3 terminal screw block
• 8AWG enamel copper wire
• 1.5mm dia 7×19 stainless steel wire (for the driven element)
• 1x 12m SpiderBeam pole
• 2 sections of a 9m Squid Fishing Pole

You can see the construction method here:

Field Test

Out in the field the mast was rigged such that the guys provided the spacing over the top of the mast giving it a peak height of 12m. Groundwave QSOs on 80m were achieved over ~20km at 59+30dB for 50W in daylight. The coil in the first run had too many turns so some more fettling is required there. We also achieved some late afternoon 40m contacts with the coil out of circuit and the driven element wound in resulting in a native 1/4 wave that matched 50ohms. No reason to think it wont tune 30m as well as 20-10m. Next steps are now to tidy up some of the mechanics and then retest with taping the coil in various places.

Once 80-10m are working, 160m will be tried with a top hat loading wire and a counterpoise radial. 160m is still an experiment and is not guaranteed. However we may be lucky.