colly0410

H & X TV aerials.

Recommended Posts

Mick, that's what's known as imaging, that's why expensive radios use what is known as "Dual or Triple conversion" to prevent imaging, the older TV's just used single conversion, so when in the presence of strong "harmonic" signals, they can be picked up easily.

Share this post


Link to post
Share on other sites

I am trying to remember the frequencies, Traffic was on VHF at the end of the FM tuner dial around 152mhz, but transmitted in AM, so off tuning brought it in fairly clear.

UHF transmission, Central Radford Road etc, I seem to recall being 452mhz or was it 433mhz. All receivable with a scanner, and was probably

that which we picked up on the TV. All now gone since Police went on to 'Airwaves' trunked radio.

I eventually worked on the Police Radio from 1975 - 1984 at Canning Circus Police Station, transmitting from the Clifford Court transmitter, that we received the Police transmissions on the TV, as a kid, some 10 years earlier...

"Canning to Panda one can you pick me some snap up from Wan's on Hartley Road, over"

Share this post


Link to post
Share on other sites

#2 - I meant to reply to this yesterday and forgot. My boy said that in Calgary (so I assume the rest of Canada) they have satellite dishes and fibre optic in new areas, pretty much the same as here by the looks of things.

#4 - Exactly, it's probably 'cos nobody bothered to take them down. or the wind never finished them off.

I remember us having an Alba TV when I was a nipper that was BBC only. When ITV came along my dad, who was in to radio and TV stuff, had ITV added which, I presume now, was a totally new receiver added to the existing BBC one. I say that because if you switched it over you had to wait five minutes for it to warm up. My mother used to go nuts as my dad would turn it over ten minutes early for football (not an every day event in those days) when she was watching something - used to make me chuckle even at seven years of age.

Share this post


Link to post
Share on other sites

The first expensive radio the ex and I bought was around 1970, it had two short wave bands and FM broadcast band plus LW and MW.

At the top end of the FM band was the police channels, when TV was crap, we'd listen to the police, so obviously on FM not AM, clear as a bell.

I believe you'll find most of the emergency services on either side of the Amateur 2 metre band, (below 144Mhz and above 148Mhz), but now becoming more and more digitized, so impossible to receive on scanners and domestic receivers.

I doubt police would use UHF frequencies, as they are affected too much by obstacles, like high buildings, we have 70cm band and it's a pig in cities, unless there's a local repeater, and even then there is still "flutter" in the signals. Best frequencies are in the 2 metre area for city work.

Share this post


Link to post
Share on other sites

All the Police frequencies nowadays are digitally encrpted ! No more "earwigging".

Share this post


Link to post
Share on other sites

I'm surprised at the use of 70cm for emergency services Mick, the higher the frequency the more problems, 70cm ham band is not the most popular due to these problems Mick.

"low" and "high" bands are the ones emergency services use this side of the pond, that is the band below and above the ham 2metre band

Share this post


Link to post
Share on other sites

Catfan, they also have started using "spread spectrum" Much more efficient than digital encoding.

Share this post


Link to post
Share on other sites

These are the ones I remember.

http://m3fon.tripod.com/freq.htm

152mhz

CH1 VHF Sherwood Lodge was Traffic in the County

CH2 VHF was special events

CH3 VHF was Traffic City and Suburbs

451mhz was Police Divisions, Central Police etc.

Screenshot%202016-01-11%20at%2020.34.14_

  • Upvote 3

Share this post


Link to post
Share on other sites

I see the police allocations on "low band" actually use part of what we have for 2metres, which goes from 144-148Mhz, the US 70cm band is 420Mhz-450Mhz.

2 metres can get "quirky" sometimes, and sometimes open up for several thousand miles, I wonder how many times UK police have been picking up US ham signals?? We usually use FM narrow band, but we are allowed to use SSB, AM and digital modes on 2 metres up to 1500Watts of power. With a good gain antenna that could equate to several thousand watts erp at the antenna. Easily picked up in the UK at times of good propagation.

Share this post


Link to post
Share on other sites

DG taxis base used to transmit just below Radio 2 on 87.5 Mhz. When I worked for Central cars I used to listen to DG to see how busy they were. A couple of times I heard the same job coming over ours & DG's radio's so knew the punter was phoning multiple cab firms & taking the first cab that showed up & leaving others on blanks. Centrals base transmitted on 169.sumat Mhz. DG is no longer there so presume it's gone digital.

Share this post


Link to post
Share on other sites

When I was running the packet radio station in Long Eaton (GB7LED) I used 2m for the downlink and 70cms for the up. The repeater was in Matlock and I could see it fine to transmit to using 70cms but not for down hence I used 2m, strange stuff this VHF.

In the 70's I sat on an airfield in Kuruman South Africa (back of beyond) waiting for my guv'nor to arrive on a Cessna. I sat listening to the 10m band on my Belcom and ended up having a discussion with a farmer in Perth Australia who was ploughing his fields at the time. This was on less than 4 watts from my car. At the same time I could hear taxis in Johannesburg 500 miles away on 2m, I thought someone was winding me up. It was skipping on every band for the best part of a day, it must have been some sun spot that day!!

  • Upvote 1

Share this post


Link to post
Share on other sites

10 metres is one of the best "long haul" ham bands, when conditions are right, when I first got licensed, a group of us used to ragchew locally on 28.350Mhz or thereabouts, one evening, pretty late, when the bands were closed, or so we thought, a ZL dropped into our group, so shows how that band doesn't always obey the rules!!

When I lived in Sacramento I had my HT with me and picked up a fellow ham in Reno on 2metres!!!!! Normally physically impossible because Reno is on the downside of the Sierras, a couple of thousand feet below the peak. There were tremendous thunderstorms that afternoon over the Sierras so his signal and mine were "ducting".

I had a packet digipeater set up when we lived in the Sierra foothills at 2400ft elevation, my radio was my dual band HT, 5 watts max on 2 metres into a "J Pole antenna mounted on the end of the house. It logged a direct link with a ham in Bakersfield, many hundreds of miles to the south!.

Again 10 metres, fair enough on the Yagi, 10db gain on 10M, I logged a feller in Mississippi from California with just ten watts of power, he gave me a 10db over S9 reading...Conditions were just perfect that year.

Share this post


Link to post
Share on other sites

Twenty metres used to get me in trouble occasionally. One day back in the UK I was chatting to a bloke on Ogisawa island on the key. I could hear somebody trying to break in and ignored it but eventually I had to listen. It came from a US frigate that was sailing in the area and he said I was bleeding on to a US Navy frequency (yes me, on 80 watts, not the guy who was a whole lot closer to him) and could I please clear off, which I did. He sent me a QSL card from the frigate though which I thought was nice even though I was never a QSL hound.

Share this post


Link to post
Share on other sites

Well i'll goo to our house'

Share this post


Link to post
Share on other sites

#38, Mick, you must have been producing some harmonics on your radio, can't see any other way they could have received you.

20M here is total ham, no military shared frequencies on that band, in fact I don't think our military uses HF anymore.

We share 70cm with the military, they have priority use of it, we second, other than that, I don't recall any other bands where the military have priority use.

I did assist in an emergency one morning years back, there was a ship in trouble in the Gulf of Mexico, mate of mine had picked the distress call up and he telephoned me to get on the radio, as the guy on the radio on board the distressed ship was using 10 metres to talk to the Coast Guard. I assisted in keep other hams from operating close to the emergency frequency.

Never heard anymore about that incident, all I remember was the Coast Guard lots the signal, my mate gave them a rough compass location, so all we could assumes was it was some idiot messing around....Carries a hefty fine and a rest in the "big house" if caught.

Share this post


Link to post
Share on other sites

#40 - Yes, it was probably a second or third harmonic but I was on a long wire which included some of my guttering which didn't help. I never had the issue again so what caused it I don't know, just lucky I suppose.

Ben - Put your mask on!

  • Upvote 1

Share this post


Link to post
Share on other sites

Never been a 20 metre fan, always preferred 10 and 15 metres myself.

Share this post


Link to post
Share on other sites

Looking forward to it Mick............

  • Upvote 1

Share this post


Link to post
Share on other sites

I remember seeing some K shaped aerials: I wonder if the straight part was a dipole & the bent bits a director, or was the bent bits a bent dipole & the straight part a reflector? I suppose both configurations would work, but I think a dipole plus director would be a few pence cheaper as it's use less aluminium. What do others think?

Share this post


Link to post
Share on other sites

I remember seeing some K shaped aerials: I wonder if the straight part was a dipole & the bent bits a director, or was the bent bits a bent dipole & the straight part a reflector? I suppose both configurations would work, but I think a dipole plus director would be a few pence cheaper as it's use less aluminium. What do others think?

Riveting though your question is Colly................I can honestly say its never crossed my mind..........or ever likely to.............lol.

  • Upvote 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...