Low band contest - Sept 19th and 20th - input please

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M0DTS
Posts: 462
Joined: Sun Feb 24, 2008 9:03 pm

Re: Low band contest - Sept 19th and 20th - input please

Post by M0DTS » Sat Sep 19, 2020 8:02 pm

Hi All,

Not the best of days out but part of the fun apparently ;-)
First off i got 15 miles down the road then realised i had for got the laptop...D'oh!
Next one of the roads right near the /p site was closed so i had to do a 20 mile detour!
Anyway, after the wrestle with the 6el 4m yagi i was on...
The PGA-103 preamp was oscillating so had to ditch that, we call PGA-103's fuses up here...

edit: Found the problem with the PGA-103 lna, the input decoupling cap to the 7805 regulator had come adrift, now fixed.
It was as oscillating ~23MHz!.

I was using SDR Angel (now that i've figured out how to get it to work) as the rtlsdr is quite low NF with the gain wound up and an old PYE filter re-tuned to 71MHz. GB3BUX was 57-59 all afternoon.

I managed one 4m qso with Clive G4FVP, this went reasonably well but not that strong.
Dave G4FRE was max 2dB over the noise and Noel 1dB so we were out of luck there.
Conditions for me were below average, Couldn't even work Mike on 144.750!

A few screen grabs attached below.
** Must prepare more for the next 4m activity **

Thanks to all who tried for a QSO.

Rob
Attachments
4m Ant.jpg
4m Ant.jpg (530.55 KiB) Viewed 799 times
G4FVP.png
G4FVP.png (501.37 KiB) Viewed 799 times
GB3BUX ~22dB in 2.4KHz
GB3BUX ~22dB in 2.4KHz
GB3BUX.png (471.95 KiB) Viewed 799 times
G8GTZ 125Ks
G8GTZ 125Ks
G8GTZ-P_125Ks.png (656.82 KiB) Viewed 799 times
G4FRE 66Ks
G4FRE 66Ks
G4FRE-P.png (419.06 KiB) Viewed 799 times
Last edited by M0DTS on Sun Sep 20, 2020 1:15 pm, edited 2 times in total.

radiogareth
Posts: 613
Joined: Wed Jan 06, 2016 9:46 am

Re: Low band contest - Sept 19th and 20th - input please

Post by radiogareth » Sun Sep 20, 2020 7:00 am

Well I tried too.....but left the whole box of 5.6GHz RX/TX/PA behind.
I did manage to setup for 4m, but was met with someone else's digital signal from 70.4-71MHz - see attached. And the PA string, which worked so well at home, refused to behave in the field. Anything over 1 watt and the waveform went very wrong. Software flakey again, SDRAngel and DVBSGui both not liking the weird digital interference. Portsdown/Lime was having trouble running power but ExpressDVB worked well but RF caused the Pluto to 'ding-dong' and disconnect as soon as I ran some power.

Good bits, I can assemble put up my 4m 5 ele LFA in about 20 minutes. (6m AGL). New (s/h) laptop has at least 3 hour battery life. WX was nice, not too windy at my location.
Talkback via my full-wave dipole worked well again, as I packed up I heard Shaun down in the Malvern Hills Q5.
Next time.....build a conventional up-converter for 6 & 4 so I can use Longmynd for RX.
Gareth G4XAT
Pics show ther digital interference and my setup. 4 element LFA for 6 didn't make it into the air on this occasion.
2020-09-19 14.52.31.jpg
2020-09-19 14.52.31.jpg (122.83 KiB) Viewed 781 times
2020-09-19 13.26.50.jpg
2020-09-19 13.26.50.jpg (78.69 KiB) Viewed 781 times

g8vpg
Posts: 353
Joined: Fri Oct 11, 2013 9:35 am

Re: Low band contest - Sept 19th and 20th - input please

Post by g8vpg » Sun Sep 20, 2020 7:39 am

I am afraid that I am going to add to the general tale of woe that this contest seems to have caused! The plan was to use Penn Hill, the site of the regional TV transmitter mast on the Mendips. Myself and several BATC members have used this before without trouble. This time the farmer arrived as soon as we had parked and told us to go. What followed was very unpleasant and upsetting and my strong advice to members is not to use this site unless you can obtain prior written permission, which I doubt will be forthcoming. A pity, because it is a lovely site.
We decamped to the Blackdown, further West on the Mendips (IO81PH33MU). Here we met a very friendly farmer, who allowed us to park in his compound off the main track. In all my portable activity, I've never met so many farmers in one day! Blackdown is higher, but has no mobile coverage, and talkback was badly affected by GB3WR and other sources. There was a very strong wind blowing all day. We managed to work Noel G8GTZ/P, a steady MER2-3 on 4m, and Dave G4FRE/P who was a strong MER13. Noel had to co-ordinate talk back from us with no Zello and Dave with no 2m. Nothing heard from anyone else. Conditions seemed poor and quite variable at times, with Noels talkback ranging from unreadable to quite fair.
It could have been worse, cold and wet may be, but it was not our best day out.
73 Shaun.

g0mjw
Posts: 1443
Joined: Sat Sep 20, 2014 9:15 am

Re: Low band contest - Sept 19th and 20th - input please

Post by g0mjw » Sun Sep 20, 2020 8:14 am

The interfering signal Gareth we seeing looks like an image to me. It's really important to have good filtering on VHF. I can see a filter bank might make a useful new BATC project. It would not be very difficult to come up with a common inline pre-amp filter for RX with a cheap TR relay. But first check this out http://www.ha8et.hu/ as Gyula has already done this for about €60.

My talkback experience was Zello was unreliable and not many took 2m horizontal talkback apart from Rob, but conditions were so bad I could not hear him. I would not even hear Noel at Walbury on my beam or colinear and it's only 30km.

On DATV I was running about 5W at the feed on both bands into a dual band beam, 4 ele on 6m and 5 ele on 4m. That gives me close to the 100W ERP limit on 4m. We are allowed much more power on 6m but I have not really built a 6m station yet and 6m used the 4m PA. I seemed to be much better on RX than TX, but that may be due to lack of interference through the tight RX filtering I have, especially on 4m where I have an 4m HA8ET contest preamp in line. The up converter I used was the one I designed for BATC, with a 400MHz LO. The driver was my original Portsdown as it does work (sort of) on 6m. In retrospect I should have used the newer Portsdown-Lime or Pluto on 4m as it does DVB-S2.

It was great to work G4FRE/P and G4CPE both ways on 4m. I managed a one way with G8GTZ/P on 4m. The puzzle of the day is Noel not being able to receive me. I also received G4FRE on 6m but he couldn't receive me. To be fair Dave had a much higher EIRP on 6m. Valliant attempts by M0DTS/P didn't result in any QSOs. I couldn't hear Shaun on 144.750 so there was little chance of DATV working. Nobody else heard on the Talkback or Zello.


Mike

g8gtz
Posts: 1363
Joined: Wed Apr 07, 2010 6:26 pm

Re: Low band contest - Sept 19th and 20th - input please

Post by g8gtz » Sun Sep 20, 2020 9:25 am

Oh dear - I can only add to the tale of woe!

I did forget the 5.6GHz transverter to do tests with Gareth plus my workbench top and vertical colinear mount but managed to work around these and was set up with 30 mins to spare!

I should have known that was bad omen - things didn't start too badly with a 2 way with G4FRE on both bands at 141Km but after that conditions just seemed to vanish. G4CPE saw me on 71MHz when I was working someone else but when we came to work we couldn't get it go in either direction despite being 90 kms line of sight and at the the same time he worked G0MJW and G4FRE - all roughly in the same direction.

I did manage a 2 way on 71MHz with G8VPG but talk back was terrible - normally it would be fully quietening - and as Mike said we struggled over a 22km path on talkback and 71MHz. I finished the day with yet another one way on 71MHz with G8LES but this time I received him!

Overall a very strange day and I do suspect my 71MHz rxr was down - I'm intending to put the 50 / 70MHz beam up at home so be interesting to see if we can get more reliable results.

Noel - G8GTZ

G4FRE
Posts: 131
Joined: Fri May 26, 2017 6:57 am

Re: Low band contest - Sept 19th and 20th - input please

Post by G4FRE » Sun Sep 20, 2020 9:37 am

A challenging but interesting outing!

WHen i arrived on site It was so windy i debated wether it was safe to put ANY antennas up. Seeing how the HF antennas of the stations up there doing the SOTA contest blowing around was discouraging. However I continued assembling the antenna and in a slight wind lull and by lying down with my feet braced against the car wheels managed to pull the antenna up into the wind. The innov 4+4 ele (unused since purchase in 2014!) had an swr of 1.8:1 on 6m and 2.1 to 1 on 4m but this was not the day to take masts up and down to adjust. Although I had the 2/70cm colinear I was not going to risk putting a 2nd mast up, so no talkback. Listening on 6m heard PA and SP beacons. On 4m heard GI GM and LX0 beacon

Had a 2 way on 4m with G8GTZ (MER15) Tried on 6m, Noel copied my signal easily but due to loud interference coming from the radio station at the bottom of the band I struggled to receive him, but eventually I copied him at 66ks near the top of the band (for my only 2 way qso). Worked G0MJW on 4m (MER6). Due to the fine work of Noel acting as a Zello to 2m transponder, hooked up with G8VPG and had a 2 way with him on 4m (MER 16) When he turned his beam on noel he was still MER8 with me! Tried 4m and 6m with M0DTS with no luck, but my 4m signal was detected!. Worked Arthur G4CPE (for the 1st time!) on 4m (MER peaked at 7.5) at 156km for my best DX. He could not copy my 6m, probably due to cross polarised antennas. Copied Noel at MER6 when he transmitted 4m at Arthur! Managed to get my 6m received by G0MJW in the final act of the day

On 4m used Portsdown 2019 +modified G4DDK nacton 437/71MHz transverter + MITSUBISHI brick (20W) +minituner. On 6m Portsdown 2019 +modified G4DDK nacton 437/51MHz transverter + 7w MITSUBISHI brick+LDMOS amp (150W, the bigger amp is locked down in wales)+ minituner

Dave
G4FRE/P IO82QJ
Attachments
G8VPG transmitting intended not actual locator
G8VPG transmitting intended not actual locator
vpg4m.jpg (222.05 KiB) Viewed 757 times
beaming at G4CPE, Malvern hills on horizon
beaming at G4CPE, Malvern hills on horizon
P9190008.JPG (1.57 MiB) Viewed 757 times
G4CPE 4m
G4CPE 4m
g4cpe4m.jpg (220.67 KiB) Viewed 757 times

radiogareth
Posts: 613
Joined: Wed Jan 06, 2016 9:46 am

Re: Low band contest - Sept 19th and 20th - input please

Post by radiogareth » Sun Sep 20, 2020 12:32 pm

Some relatively 'easy to build' band pass filters on this page, 2m shown but links at the bottom of the article to 6 & 4. Wouldn't be hard to stick one of the eBay modamp boards either before or after to help curtail the losses.
https://pa3csg.nl/?page_id=61

Gareth

G4FRE
Posts: 131
Joined: Fri May 26, 2017 6:57 am

Re: Low band contest - Sept 19th and 20th - input please

Post by G4FRE » Sun Sep 20, 2020 2:05 pm

As i mentioned to Mike yesterday, Downeastmicrowave now do a range of bandpass filters, both SAW and Helical from 50Mhz to 2400MHz. https://www.downeastmicrowave.com/Band- ... em-bpf.htm The helical 50 and 70MHz have worked well in previous projects

Dave
G4fre

G4FRE
Posts: 131
Joined: Fri May 26, 2017 6:57 am

Re: Low band contest - Sept 19th and 20th - input please

Post by G4FRE » Thu Sep 24, 2020 9:48 pm

Spoke to Steve at DEMI earlier. The 50/70MHz helicals he uses are from Temwell in Taiwan https://www.temwell.com/ . Looking through their catalog/price list the 50MHz 2 pole is around£12.50. Steve did say he would sell the filters are avaiable unboxed (ie filter+pcb) if people wanted to squeeze them into existing projects

Dave
G4FRE

M0YDH
Posts: 215
Joined: Sat Dec 31, 2016 5:59 pm

Re: Low band contest - Sept 19th and 20th - input please

Post by M0YDH » Sat Sep 26, 2020 1:36 pm

Perhaps we can try this again in the Spring? I shall likely set up somewhere closer to Oxfordshire than Shropshire.
What is the 6m transmit frequency for ATV please?
Out of which port on the 4 way switch of a Portsdown 2017 does 6m TX emerge?

73
David

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