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The Great GM Microwave Extravaganza


Thanks Andy and Jack - nice group.


Hi Stuart

I’m hoping to be on a summit for the next 23cm UKAC as well, it was good fun last time - I look forward to an S2S.

Picking up Andy’s comment from higher up the thread about FM activity on 23cm, I have had a couple of QSOs on FM using the transverter, with the operator at the other end using a Handy and rubber duck.

I haven’t yet bought into 13cm, but I agree that there is a lot of scope here for activity to grow…


Another great day out on 13cms working S2S - (GM/CS-001 to SS-158), especially with the wx being so good.

If you would like to have a ‘shifty’ at our escapades checkout this POSTING on our GM13 chat site. All great fun :grinning:

73 all



Oops! Made a bit of a mistake on my last Posting in that unless your registered with us on GM13 ye canny see the pics. Doh!

So knowing how you will all being waiting in great anticipation I’ll add a few pics here.

GM4COX’s kit used on GM/SS-158. The SG transveter running about 1W O/P and 8 x 1.2v NiMh battery pack are both located in the blue bag. The transverter is being driven by my Vx8 (in the black bag hanging from the fence) running about 700mW on 432MHz. The aerial is the pcb 4el supplied by SG Labs (a SOTA friendly - 21el is in the making) suitably modified to just slip over my SOTA pole.

This is Paddy MM6IPO’s set-up (note the 4el connected straight to the transverter) in his high flat location in Glasgow - IO75TV. Because of Paddy’s licence limitations on 13cms we worked crossband 57-13cms/57-2M - FM. And not a LOS - 60Km path. Amazing!

And this is a shot of my LOS S2S contact with Jim MM0GLM on GM/CS-001 (just over 100km) 59 - FM both ways and superb FM quality which are now becoming used to on 13cms.

All-in-all both contacts were a great success on a superb day to play radio :relaxed:

Till the next time.



23cm antenna?

I decided I need a 13cms fix and with possibly the HF conditions being poor after the X class flares, 13cms would work nicely if not much else would. A message to the gm13 reflector got replies from Jack GM4COX and Jim MM0GLM. Jim was going to Stronend SS-163 which is LOS to anything in the Pentland Hills. My choice in the end was Scald Law SS-125.

I parked and booted up and having made sure I had all the gear (I nearly left the good 13cms antenna at home) I set off up the easy walk. It starts gently but the final km is steep. I did this for the first time in December 2006 and the effort was nearly enough to kill me. No excercise for 30 years meant I was an unfit slob. It took 1hr30 to summit. Today after 11 years exercise and some 12-14kg weight loss, it took me under 45mins. That made me feel so pleased any 13cms QSOs would be a bonus!

I’d arranged with Pete GM4BYF for him to be QRV. He lives at the foot of Allermuir Hill SS-171 and there 400+m of rock between him and Scald Law but only 5 km or so. Must be doable on 13cms. I called for Jack on 2m and also tried to see if Jim was QRV. I was bushwacked by Christine GM4YMM and Ken GM0AXY on my appearance on 145.400. 2 QSOs. Then Steve MM0XPZ called from Greenock and that was 3. I found Colwyn MM0YCJ/P up on WS-021 in the Grey Corries for 4 QSOs on 2m and that was the hill qualified. Finally I found Jim in QSO with Andy GM8OEG. 2 more QSOs and S2S contacts.

I QSY’d to 13cms and Pete GM4BYF was an easy QSO. Whist waiting for Jim to setup on 13 we tried experiments with different antennas at Pete’s QTH (67ele Yagi vs 10db Horn) and also trying for reflections. A reflected signal from the Moorfoot Hills (Meikle Says Law, Spartleton etc.) was a better signal that the direct. But I reckon the direct signal was lots of scattered signals really with the amount of rock between us. Jim called in off the back of my antenna was S8. He was louder when I pointed at him!

OK I tried for Jack and it was hard going. He gave me 52 but he was barely there, 31-41. We completed the QSO but it was a struggle. It was later I learnt the path was not LOS at all, I thought it was but hadn’t checked. I was worried Jack may have a TX problem with the transverter but it was a poor path and a nearly flat battery. Phew!

I QSYd back to say Sayonara to the others as I was chuffed out with 3 QSOs and a fast ascent and wow! Wow! Wow! Dan GM6CMQ, a member of our VHF contest group GM3HAM, was in QSO. He’d seen the messages on the gm13 reflector and knew Scald Law is LOS. He was my 4th QSO on 13cms and I qualified on 13cms. That gave me a wonderful feeling.

We’d had a shower early on and the WX did not look good so I packed everything away and made a fast descent to the car. I did have a problem with the semi-rigid feeder to the antenna due to poor design choices I made. I have fixed it for now but I need to make another antenna that avoids this stress point in future.

A few spots of rain after a slight shower. Beaming at GB3CSB on 2320.985. This is the work of Dave Anderson GM6BIG (the first QSO I had with GM on 70cms in 1990 when I lived near Liverpool was with Dave). I will buy him a beer for building this beacon as it really makes 13cms SOTA viable here.

The SG Lab transverter in a plastic bag. Connections are antenna, RX antenna, power, 70cms IF, PTT lead. The funny bit of UT-141 in the antenna lead makes the SWR just peachy.

The antenna on the pole. The sky looks really threatening but it did improve a lot during the activation.

A much better sky near the end of the session. This is looking towards Dan GM6CMQ’s QTH in Fife.

The new Queensferry Bridge and the old Forth Road Bridge. Another of our contest group was schoolboy and attended the opening of the FRB in 1964 and the 50th Anniversary in 2014. He also managed to get a ticket to walk across the new QB before Brenda opened it earlier this week.

Hmmmm… some rather wet WX coming my way, time to go.

The still lovely WX as I descended as quick as I could. I didn’t want to get wet!

This was a great on the spur of the moment event. I’m really pleased at how we can manage to get lots of activity on a band under threat. It just needs a few people to keep going out and playing on these bands to persuade more peope to come and play.

With the sun being a bit broken, microwaves and VHF/UHF will still work. It’s well worth you and your mates considering buying a job lot of gear and organising yourselfs into activation squads.


Good one Andy,

And great to work from the home QTH (kit set-up on back patio for a better path to the East from my QTH)

And I think your right - it was the ‘CLIMPY’ Wind Farm that was causing the - phaff, phaff, phaff on you signal (as per our discussion on GM13) and great enhancements with the planes taking off from Edinburgh.

If I can get my ‘beastie’ back on the road should out this coming weekend on 13cms.




That’s a great result being able to get 4 on 13cm.

Looking forward to another 13cm contact with you guys when you’ve a potential path to GI. I do need to sort out a Tupperware box/pole arrangement like that there though. On the last outing it was just sitting on a box on the ground in the sun which worked fine but that’s not normal hill weather :slight_smile:


Another weekend of dubious weather. Forecasts for SW Scotland today are for heavy rain so no chance to finish off my SS bucketlist. NE (Ballater way) was forecast to have light rain though today that has changed to dry. Can’t win them all so another local activation aiming for 13cms QSOs was on. I don’t intend to do much 13cms during the Winter, ordinary HF is hard enough in cold wind and snow, so I want to get as much in now before 4-5months enforced shutdown. With 6 non-SOTA stations within 30miles of Edinburgh QRV 13cms, the chances to get 4 QSOs are high. An alert was pushed out to the GM13 group. Jack GM4COX and Dan GM6CMQ were up for a play so there was an S2S chance.

My summit was Black Mount SS-158, a Pentlands outlier. I remember toiling up this thinking it was a serious mountain assault akin to scaling the Eiger when I started SOTA in 2006. Now I just threw the SOTA box in the car, drove out in 30mins, put on boots and walked straight up it. Just over 45mins from locking the car to getting the handy out to call Jack. Well I dropped my rucksak on the 13cms antenna doing that and bent it, straighted out it worked, but the elements need tweaking as the SWR is more than it was pre-bending :frowning:

It was a blue and sunny morning but by 1300Z it was a black sky. And windy. I didn’t notice that on the forecast and that made antenna aiming hard. Onto 13cms and Dan was weak…how can this be? Well from Scald Law I could see the Forth and the bridges and Dunfermline where Dan lives. Now I was 10 miles further away and behind the main Pentland ridge. Pointing directly at Dan and he was 59+ but it was possible to drop his signal to 51. This wasn’t possible at Scald Law, 59+ wherever I pointed. Jack was not strong unless I pointed his way when he was 59+. I could see Dungavel Hill SS-165, well I could at the start, the clag was down on Jack. The wind was also affecting Jack, he was hand holding his beam and so it was easy for it to not be pointing exactly at me as he operated.

At this point I was happy. Well sort of. A 13cms S2S, A 13cms QSO to a fix station. But it was quite cold and the clag came down making it seem much more like November than September. Also my bag was in Summer configuration and I could have done with another fleece. At this point Brian GM4DIJ appeared from home on 13cms. Despite being well screened behind the Pentlands he was an easy S3 signal. Just too screened to work Jack who had not only the Pentlands but was stuck behind 200m of Tinto Hill overtopping him in that direction.

We all chatted for a bit and then closed down on 13cms. I looked and saw I needed 1 more QSO to qualify. I was too cold to setup HF but I thought must be able to get a QSO on 2m. I knew Robin GM7PKT was out and hoped he’d still be on air. Onto 145.500 and I hooked up with Robin and Steve MM0XPZ. An S2S with Robin was great as I completed Carn nan Gabhar ES-022, an infrequently activated summit near Braemar. Robin was more pleased, it had taken him 3.5 hours to work 4 contacts. After Steve was logged I packed up and was back at the car in 30mins where promptly the cloud broke up and the sun came out.

Another great day on 13cms including working a new station. Again no earth shattering DX but I have yet to try 13cms from a summit and fail to have at least 1 QSO. For a band that has low occupancy and use I think that’s pretty amazinf going. And again, I’m always impressed at the silly distances you can work summit to summit with a 2m handy and a rubber duck. 140km upto Robin being an example.

Finally congratulations to Paddy MM6IPO who is now 2M0IPO. Paddy has one of these 13cms transverters and has been working to upgrade his licence so he can join in the fun on 13cms.


Yes another great day on 13cms - if not for the wx - specifically the wind! Interestingly when I returned home Anne said it have been fairly calm, and even talking to David GM6BIG at his home QTH whilst I was on the summit, Dave said it wasn’t too windy. This is a familiar phenomenon I have observed where all you need is to rise a few hundred metres and your into the ‘wind-zone’. You can see this whilst standing at a low altitude with next to no wind - by looking up and see the stratus clouds scudding by.

And a pity you couldn’t hang around a bit longer Andy for the forth 13cms contact with Paddy. The path will go from SS-158 to Paddy, though it’s not LOS, I worked Paddy cross band 13cms/145.4 59/59 - FM.

Path profiles ready to be loaded up to GM13 later today (25th Spt).

Cheers all



That is an often noted anomally in gravitational force, whereby a relatively large mass such as a rucksack is strongly attracted to a delicate body such as a 13cm antenna. We humans have a subconcious primeval knowledge of this, as the manifestation is often followed by the thought “I knew that would happen” :smile:

All good stuff on 13cm, and hats off to Robin for waiting 3.5 hours to qualify!



I finally finished another 13cms antenna started some time ago. This is a double-double quad. In theory it has 3dB more gain than a double quad. GB3CSB is clearly audible from the downstairs shack window, from the upstair spare bedroom it romps in. A simple comparison shows that GB3CSB peaks at best at S7 on the double quad and S8 on the double-double quad. The built SWR meter on the SG Lab transverter gives a solid green display from 2320MHz to 2321MHz.

Like its smaller brother, a Chicken Chow Mein container from the local Chinese take-away is used as a radome to protect the element when out portable. The container is transparent to microwave oven RF which is about 200MHz higher up the band that the amateur allocation!


Hi Andy,

What are the connections at the feed point? If the conductors radiating from the feedpoint from top left, going clockwise are labelled A, B, C and D, are conductors A and B joined, and C joined to D at the feedpoint?

Also - is the length of each square a full wavelength without any end correction (like on other loops)?


Andrew VK1DA/VK2UH


It’s a short circuit at DC. The coax inner goes to the bottom and the outer to the top. Each quad is1 wavelength long and it’s the inner length of the loop is important as is the separation between the reflector and element. On the double double, there is a crossover and the elements do not touch.

Those pictures show the antenna vertically polarized. Like waveguide these seem to be back-to-front!




Does anybody use the 23 cm SG transverter along with an FT-857? I wonder i f the rig produces spikes at the beginning of a transmission that could damage the transverter.



Good morning Pom,

Users within the Scottish 13cms Group - GM13 in the main use the SG Transverter with it’s ideal companion the FT-817. The SG produces a max of about 2W @ 13 with a 70cms input power of about 1-1.5W. (I have my 817 set at about 800mW producing just over 1W - best battery consumption levels for both the 817 and transverter) so ideally you would have to reduce the 857’s 70cms to around these values. Is it possible to reduce the 857 to this sort of level? If not you could build a little external switching cct to introduce about 10dB attn to the 857 Tx’s output.

And wasn’t aware the transverter had such a problem. I wonder how you discovered/uncovered this problem. What technical issues we have found so far have been highlighted on GM13.

Trust of some help.




857 causing spikes not the transverter Jack. I think it may be related to how the ALC works to reduce the power out on the 857.


Oops!, should have read Pom’s Post more carefully. That’ll teach me for not rubbing the sleep from my eyes :sleeping:



The 857 will reduce to 2 watts on 70cm.


:grin: 3rd double espresso here in the office Jack and this morning’s crop of daft emails now dealt with. Time to see why last night’s regression tests didn’t run…