RADAR

[G0DJA]

Why does nobody openly admit to the fact that, on the 23cm band at least, you probably will get interference from RADAR on your picture?

I'm told that, now I've invested in a 2.4GHz unit, I can also expect problems from WiFi units as well. Oh, great, maybe that would be another thing that future ATV people might need to know before they spend time and money on these bands...

Please understand that these limitations might not put people off, as long as they know about them and can plan to mitigate for them in future.

Pretending that they did not exist before people buy gear is a certain way of P*ssing people off, In my opinion. OK, I'm now finding out about these issues. If I'd known before, maybe I'd not have bought in, but nothing that I had seen before spending my money alerted me to the possible issues...

Maybe this is why people don't 'do' ATV? As in, by the time you've found out that you've bought a lemon, it's too late?

Dave (G0DJA)

[M0SAT]

Hi Dave

Don't know that there is any "cover up" hopefully newbies will now be able to visit this forum and see some of these comments and make some informed decision with up to date information and discussion.

My recommendation to anyone is to try and get onto 10GHz, no radar, no wifi, no nothing, other than clear BBC quality ATV unless you don't happen to have a 10GHz repeater in range in which case there will be "no nothing!".

73s de Dave

[G0PVR]

HI DAVE, sorry to hear you are getting problems with radar, it can be a pain, there are some excellent interdigital filters available , to help with the problem, see cross country wireless, or visit my website and look under atv, for full details. these realy help with interference onboth 23cm and 13cm, however the inband radar is a problem, a big pain is clee hill radar, this can be seem country wide as a series of 8.2 second splashes on your picture....we have to live with it , but it is a nusence.. dont give up, i get superb pics and, can use both 23cmand 13cm with little problem...be resiliant and you will reap the benifits john g0pvr

[G0DJA]

Thanks John, sorry for the delay but your reply seemed complete as it was...

I've looked up various interdigital filters and other bandpass designs, so I have a few reference points as well now.

RADAR still continues to be a major inconvenience, at times making it too distracting to carry on watching the signal from the 'local' ATV repeater. Especially when all that is being transmitted is a test card, but that's another issue.

Following my experience on the local net last Friday, I've all but decided that my ATV activity will now be either /P in contests, or from special event stations. After my initial enthusiasm lead me to buy 23 and 13cm boards, and even look into how to modify the 13cm units, I've now come to the conclusion that the locals don't want newcomers with simple gear on 'their' band. So, I'm not going to use their private, local system. I'll 'do' the contests and maybe even try to activate ATV on special event stations instead, but I wont trouble the locals who don't really want to see my pictures from here.

[G0PVR]

Ok dave, sorry to here about the clique, in your location, fortunatly we have no such problem here, that kind of thing has no place in ham radio, people wonder why, there is little activity on tv!...you watch the contests dave, i bet they are all screeming for your contact then!!...I did portable last year because i had not got the rotator or antennas up then, its great, but you will need the filters, ...the problem is , we usualy go to a high pearch for the portable useage, unfortunatly, so does all the 3g, phone systems, pmr , etc...good luck and its great fun to get on a hill for a few hours, ..let people know via the forum when you are going, you will maximise the contacts!! good luck john ...
see my atv streaming video, usualy gb3ud, or my mug in the shack...on
http://g0pvratv.camstreams.com

thanks john g0pvr

[G0DJA]

Hi John,

Yes, I can imagine that a high spot next to all the other RF services would cause problems. I used to get breakthough onto my old FT290R when I was out with the WBFM 10 and 24GHz gear.

I watched the Friday 'net' last week - 1 person put a signal up...

However, on a more positive note, I did manage to talk with a couple of the guys who use GB3KM via 2M FM on 144.750MHz and even heard my own audio coming back down the internet from their talkback system on the Ustream website. Which was quite entertaining, if a little off putting due to the delay.

I've designed some yagis for 13cm, which I intend to build before the next contest, and will box up the 13cm Comtech boards as well, but I am now looking for either a DC powered TV receiver, or a small 12V to 240V DC to AC converter to power up one of my small domestic TVs. I also need to properly box up the 15 Watt PA and changeover relay, as the strain on the leads with it being a temporary lash up is causing me concern. I just need the right sized box.

[g3uvr]

Dave.. Just found the site and wish to add a comment on radar. Sitting on top of a hill here and pretty well sited RF wise I dont have the problem you seem to think exists on 23 and 13cm..

On 23 the Radar is very stong in the middle of the band around 1265mhz when I beam to the north. At the top GB3UD and GB3TM are radar free. Also at the botton of the band 1249, 1255 no problem. I do not have a filter only a preamp feeding a Zeta 1000L satellite RX. I have tried other Sat RX's and do admit some are more prone to Radar problems than others.

As far as 13cm is concerned, yes above 2400 can be a problem with WI-FI. I use around 2335mhz it fits in with the bandplan with no WI-FI problem. Here I use a Preamp DB6NT into a home built Bob Platts down converter into a Zeta. Also my 13cm narrowband ariel still has some reasonable performance at 2335. I have tested from my home QTH the DB6NT Kuhne 13cm downconverters and found that the wideband version cant be used due to breakthough from 3G phone base stations. The wide band converter does not have any filtering and suffers image problems from out of band signals at 2150mhz as far as I am concerned its not usable if you have a nearby 3G mast without external filtering. The other narrower version with internal bandpass filters works ok.

Hope this info is of use.

Denis G3UVR IO83KH SJ269820

[G0DJA]

Thanks for the reply Dennis,

I do have other 23cm equipment for SSB/CW (in fact, I use the antennas for Cw/SSB for ATV as well) and, other than when conditions come 'up', I don't get much of a problem with RADAR as I do when I use ATV.

I have a borrowed Wood & Douglas unit, which is very good, but needs my mast head preamp in front of it for full P5 pictures, and a set of Comtech boards for 23 and 13cm. RADAR seems, to me, from this location (170m ASL with a reasonable take off from N clockwise to about 160 degrees, where the ridge that runs south from here rises up a bit) to be a problem on ATV.

I can sit with the output of GB3VL playing and the 'clash, clash' and vertical bars on the signal are always noticeable. Whereas, I use Spectrum labs to dig in the noise on CW with fewer problems from RADAR.

Yes, I am aware that ATV is a much wider mode, and more prone to wide band RADAR interference, and many repeaters have moved their input frequencies up to 1280MHz to try to avoid the worst of it, but this is the sort of thing that newcomers, in my opinion, ought to be able to find out before they spend money. After all, they might decide to have a go anyway, but to sit with the 'clash, clash' noise going gets on the nerves quite quickly, in my opinion.

There's been a call for encouraging newcomers into ATV. Well, I'm a newcomer and I don't yet feel very encouraged to keep going. Apart from the enthusiasm of M0DTS and G1LPS and a couple of other local stations it seems very, very quiet on the talk back frequencies and there's very few stations who seem to come on very often. Even in the Summer Fun ATV Contest the only signals I heard on the talk back frequency were M0DTS/P, and they were just a bit too far away to swap pictures with. In another part of this forum a station with 44 years experience says he made 1 contact during the contest. I used to do better on 10 and 24GHz WBFM in the 1980s. Unless the gear went faulty, if I made less than 5 contacts I considered it a poor day, but to make absolutely no contacts in what should have been, if not a contest at least an activity day, seems a very poor showing to my mind. Perversely, on other bands, contests seem to be the bane of peoples lives, cluttering up the bands on a weekend so that they can't get on to work a few people normally, how different the ATV contest was on 2M talk back and on 23cm at least.

I'll not mention the fact that some locals seem to dislike my 'too easy' entry to the mode using Comtech boards, as that's another reason why I would hesitate to recommend the ATV mode to anyone else...

[G0DJA]

Update:

RF Conditions are so poor today, that the RADAR interference is slight. Hooray!

However, this is offset by the lack of any other station on the band, as seen from here...

I've transmitted through GB3VL, holding up a card with my call sign, my locator and the 2M frequency that I'm listening to (144.750MHz FM) and the question "Anyone About?" but answer came there none...

[G0DJA]

Oh, hello.

G0ACZ in Matlock via GB3VL. Says he's listening 144.750MHz. Great, someone to work on ATV.

Ah, as soon as I call him on 144.750MHz and transmit through VL he does not reply either on video or 2M FM.

Perhaps he doesn't want to work me.

Oh well...