It looks like I have the new ball on this topic so here goes...
I recently discovered I was causing TVI whilst WSPRing on 2.
Perhaps I should explain my situation. Where I live we have local TV translators covering the five networks.
I have no problems with them.
However our location is such that reception of Melbourne TV is possible with a Y13 antenna and a masthead amp, producing reasonable signal strength and good signal quality although at times prone to ignition or powerline noise.
It was ch7 that was being wiped out by my 5 watts of WSPR on 2m, ch9 less so and ch10 slightly. Operating on any other band on any mode is TVI free.
I installed a Kingray FL3BPMH filter but it had no effect.
I installed a stub cut for 2m...no effect.
I thought my IC7000 might be in trouble so tried my IC706...same result.
I am now thinking that perhaps the ageing half wave vertical I am using is the problem.
Unfortunately it will be a major operation to replace it but it seems inevitable.
Anyone with different ideas?
73 Nev
Maybe have a look at the telly co-ax and splitters (if fitted). If its not RG6 and in good condition is has to be suspect as a contrbuting factor.
Hello Nev,
okay now the fun begins, was the Kingray filter ahead of the mast head amp or after it? If it was not in front of the mast head (between antenna and amp input) then you could expect less effectiveness as it might be the mast head amp is seeing an overload condition from the 144.489 RF.
As a test could you try some dummy runs on CW carrier or FM (unmodulated) on differing frequencies across the 2Mx band to see if there is any particilar part of the band is worse or better. I am thinking it might be worse as you move up the band as you will be getting closer to the TV freq.
I have a similarly weak TV signal at home but no translators we can use and at times we loose free to air all together and have to rely on a VAST satelite feed.
Depending on how cluttered your horizon looks ( I look into a ridge at home for TV ) then a change of antenna for the TV may bring supprising results. We went from a long boom yagi to a modern version of a phased array, which yielded us amazing improvements.
With one of those kingray filters in line, before the mast head I can run full power on 50 & 144 with no scream from inside the house, I took the filter out for a few weeks when we changed antennas to the phased array and within days was in the bad books from even running 25 watts on SSB. You can guess it did not take long to put the filter back in line.
Hope my rambling helps.
Regards,
Peter, vk5pj
VK3LU Wrote:I installed a stub cut for 2m...no effect.
Open circuit quarter wave or short circuit half wave coax stub and was it at the the input of the masthead amp or the input of the TV ?
VK3LU Wrote:However our location is such that reception of Melbourne TV is possible with a Y13 antenna and a masthead amp, producing reasonable signal strength and good signal quality although at times prone to ignition or powerline noise.
You best have low expectations of resolving any TVI with such low signal levels and TV set front end and IF gains near maximum. The ACMA would most likely tell you that the local translators are the only source that should be utilised, the same as happened on the Gold Coast (SE Qld) when the Mt Tamborine UHF TV translators came on line.
73 Doug VK4ADC
Peter,
The filter was ahead of the amp, naturally. Anywhere on 2m causes the tvi.
Incidentally, I got the idea of using that brand of filter from a thread of yours on the defunct forum!
Doug,
The quarter wave stub was at the input of the filter.
I have absolutely no intention whatsoever of involving the ACMA. Pointless. I am fully aware of the fact that they would tell me to sod off and stop annoying them and watch the tv from the local translators that were provided at great cost.
However, we do watch tv from Melbourne because we can, and because the quality of the picture on the commercial channels locally is not as good as the Melbourne tv because it arrives here via being at the end of a string of off air hops. The ABC and SBS are excellent, as they are delivered by satellite directly to the translator.
During the next week I am going to try a mobile 2m antenna on a magnetic base on the roof and see what happens. Will keep you posted
73
Nev
I tried the mobile whip on the roof and the result is the same...TVI to ch7.
So, if a filter and a suckout stub don't work then I am thinking I might need a 2m braid breaker.
Off to mister Google and see whats there.
Cheers
Nev
Hi Nev,
it does sound like you have a real teaser there with that problem, I had thought it was a case of mast head overload but seems not to be the case if the filter is ahead of the masthead, it should be peeling down the signal from the 2 metre band quite well. I know it may be difficult but is it possible to test reception without the mast head inline? hoping there is enough signal there to give you some signal lock on DTV as when you say it happens all across the 2mx band it screams at me it is mast head overload but hey I am not the one on the ground trying to fix it so sorry if I sound like a one track record
Yes good idea on the braid breaker, it may be some common mode currents that are causing the TV to hiccup in the presence of the WSPR Tx.
best of luck in your investigations, sorry you did not get the same benefit as I did from the filter.
Regards,
Peter, vk5pj
Hi Peter,
The braid breaker idea is a last resort, I am afraid.
Luckily I found a commercially made one in the junk box. I have had it for years but didn't really know what it was. I pulled it apart to check its construction and sure enough it was one.
So as soon as I get the chance I will install it and see what happens.
I will keep you posted.
73
Nev
Peter,
I tried the braid breaker but unfortunately it didn't work.
So the Kingray filter plus the braid breaker, plus the suckout stub do nothing to stop the TVI on ch7 when I tx on 2m WSPR at 5 watts. No other band does it.
I am at a loss to explain why.
I will give 2m a miss for a while while I consider other possibilities.
Cheers
Nev
Hi Nev,
Thats a shame, cant help u further personally.
You could just run ur 2m WSPR RX only, or set up for 6m WSPR as its been going quite well lately, esp yesterday
Hi Leigh,
Yes, it's a bit of a pest. Unfortunately the amp gain is only adjustable between 22 and 30db and its running at 22db which produces excellent signal strength and quality
I would like to get 3db and 6db inline pads and have a fiddle.
Yes 6 has been good lately. Interestingly, all my spots were in a north east direction while others were getting them from all directions.
WSPR is an interesting mode!!
Catch you on WSPR
Nev
Whats the grounding on your 2m antenna & TV antenna like? Have you tried a 2m bandpass filter on your transmitter? How far is your half wave vertical physically located away from your TV antenna?
As Peter said, I think it's overload on the masthead preamp. Try another antenna without the preamp. I've found the log periodic design to work well, even down at VHF.
There are many things to try before giving up. It would be good to have another 2m WSPR station.
Also another thing to double check is that your WSPR TX signal is clean (not being overdriven etc)
Hi vk7hh,
I have 2 more things I would like to try. First is trying an attenuator at the input of the amp. I am thinking of perhaps a 3db and a 6db F type attenuator and try them at the input of the amp to reduce the overall gain down from 22db which is the minimum setting.
The other is trying another amp I have. Same make, different model.
I don't think it could be the TX as I have tried two different ones.
Just looking around today I find that the only people with antennae for Melb TV are us!
The others are quite a few houses away. I might just not worry about the whole thing and TX WSPR anyway.
Nev