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The Great GM Microwave Extravaganza


#46

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.

C-ya!

Jack(;>J


#47

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:


#48

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.


#49

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

Jack


#50

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!

73
Adrian
G4AZS


#51

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!


#52

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)?

Thanks

Andrew VK1DA/VK2UH


#53

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!


#54

Thanks


#55

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.

Ahoi
Pom


#56

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.

73

Jack(;>J


#57

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.


#58

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

(:>J


#59

The 857 will reduce to 2 watts on 70cm.


#60

: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…


#61

Now Brian, it kinda makes sense as per Andy’s statement about the RF level control and trying to reduce the drive to produce such a low output value from PA and potential instability?

(:>J

PS: Now on my second cuppa tea after my bowl of porridge ‘Goldilocks’ :bear:


#62

I suspect the question re the way the FT 857D behaves is related to the known issue with the IC 910. When you put the output to say 10W and hit the PTT the 910 may briefly output 100W and then ramp its power back to the set 10W. This can damage a transverter if it cant handle a brief burst of 100W.

An FT817 is unlikely to produce 100W but a FT 857D can.

Compton


#63

Thanks, Jack. Compton almost put his finger on it. And Andy pointed out the issue I’m talking about. :slight_smile:

As most modern TRXs the FT-857 regulates P/out with the ALC. This may result in spikes of full power at the beginning of a transmission, what would be 50 W on the 2 m band. 10 dB more than the specs of the sg-transverter, though the FT-857 can be set to 5 W and even lower if you adjust the lower P/out in the service menu. I don’t want to be the first to roast the sg by using a high-power rig.
On the other hand I don’t own an FT-817 but an old FT-290R (5 W w/o PA, 25 W with PA, -3 dB against the 857). I would rather have only one rig to schlepp up the summit for both, 2 m and 23 cm.

Yes, I know, driving the sg with a FT-857 is like shooting sparrows with canonballs.

Ahoi
Pom


#64

It is possible to make a limiter that removes the spikes. Thinking on my feet may be back to back (series) diodes. That conduct at say 6W or so. In normal use they’d be high impedance. I’m sure this issue must have been solved by transverter users using other ALC limited QRO rigs.

You’d gain bonus points from me for using an old school 290 with a very modern transverter. :grin:


The Rather Tiny DM-rowave Extravaganza
#65

The FT8*7 series has three power levels that can be selected in each set of bands. The 6m, 2m and 70cm bands each have their own settings.

For each power level, there are two settings, one being the output power and the other more important one being the RF driver gain.

If the 2 watt level has been configured correctly, the radio won’t be able to output a 50w spike because the drive level will have been set appropriately, so that the radio will only just make the power level set as the maximum ie 2w.

If the user performs a super master reset, all the control levels are set to max. In that situation, all power levels are the same. If the power is cut back using the ALC setting, leaving the gain set to maximum, the 857 is then capable of a 50w spike followed by the gain being reduced by ALC to the preset output limit. IMO these power controls are more suitable for FM modes than SSB. Using the radio to drive a transverter is outside its designed application, so some extra research is advisable.

The bottom line is that if the radio has been configured using the factory procedure, and you set it to a lower power level, eg 0.5w or 1w in the case of the 817, you should not get any power spikes higher than the nominated level.


The Rather Tiny DM-rowave Extravaganza