CB/11m reception

Crazy Ivan

Hi all,

so inspired by another thread about the health (or lack thereof) of CB in Ireland, I decided to dig out the old scanner and have a poke around to see what the activity is like around Galway. I'm using nothing overly fancy to be honest - just a Yupi MVT7100 with a VHF whip.

Now I know that this isn't the greatest antenna for ~27MHz reception, but I thought I might hear something. There was, as expected, nothing (nada, zip) on the usual AM frequencies (26.995 - 27.405), over the last few days at least. I was clinging to the hope that reasonable people *might* have started into the roaring 40's again. I haven't see any kind of mag mounts etc on a single[\U] boy racer's car around here in years.

Someone had mentioned that the Hotel Romeo group and others are working away on USB and I have seen on other posts/forums that frequencies like 27.515 and 27.555 (or just 555 as people seem to call it) are supposed to be fairly active. Anyone mentioning these frequencies usually also states that people are working all 32 counties from the midlands for instance.

When I try these frequencies in the evening/night time, I can't seem to get anything at all and I'm wondering if it has more to do with my set-up. I mean I know it's fairly basic for now, but is it so completely unsuitable that I wouldn't hear a peep? My antenna is obviously grossly lacking. In saying that, I can often hear Hamburg Met RTTY feed on 10.1 MHz with nothing more than this whip. If I mounted an external, or even used an old CB mag mount I have lying around, should I get more of the midland activity? Would a matched long wire be more suitable? Or is there just little to no activity at these frequencies receivable in or around Galway/the west?

Might be getting my hands on an unmodified FRG-7 soon and I believe that has coverage up to 30MHz (AM and SSB) so it might be more suited to this kind of thing. I'm thinking of getting back into the hobby, but I have given away, dumped or lost a lot of my equipment over the years and I don't really want to invest much if nobody's on there to talk to. Are there any good radio rallies on in the next while where I might find some (cheap) second hand rigs/antennas?

watty

Limerick Rally in the new year.
You ought to at least hear the Mass on Sunday.

A discone on the roof is much better than Whip (7MHz to 2.5GHz receive and 11m to 1.3GHz transmit).
A 2.8m long bit of washing line insulated by at least 30cm of plastic cord/rope holding it up at far end and at feed end.

Crazy Ivan

Excellent! Thanks a million Watty. This is the kind of info I'm after.

On the holier side of things (that would be an ecumenical matter, a la Fr. Jack) weirdly the local chapel transmits inside the normal broadcast FM range (88-108 MHz). This is only at mass times and only for Sat and Sunday masses I think.

God knows how they get away with that one (pun intended) although they may have some kind of license. I'm not up on all of the licensing laws!

Any good discone retailers around? I have a Long catalogue and they seem to be here for ~85 or 90 Euro. They are quoted at 25-1300 though. I already have something that will cover that but my interest is starting to lean towards HF so long wires it is for now! Is there an equation for calculating long wire antenna lengths so that they're tuned?

Any idea when Limerick rally will be? I don't see anything about it when I google.

northdublin

check out www.frequencydb.com great site dedicated to hobby radio in ireland. on the dipole idea the thicker you have the wire that you use to construct it the wider the band width will be....ie it will be more resonant over a wider frequency range and if posible use heavy duty coax like rg-213....not the rg-59 light stuff.

watty

A little knowlege is dangerous.

At VHF/UHF thicker wire will do what you say and RG213 is better. At CB frequencies, no.
You'd need about 6 wires arranged in a 30cm cylinder pattern to broaden aerial wire or dipole. Google "Caged Dipole"

RG59 = 75 Ohm
RG58 = 50 Ohm

You'd need to have a 100m run of coax at HF to worry about RG213. Of course if you have a 1KW linear then the RG58 might not take the voltage. RG213 then.

The RG213 is OK for 144MHz, but for longer runs at UHF, you want LMR400

Crazy Ivan

northdublin wrote: »

check out www.frequencydb.com great site dedicated to hobby radio in ireland.

Actually I've been trying to register for the last while but I can't! I get to a stage where I get an email telling me that I have an account which is inactive until the admins "OK" me, but no further. I never get the email saying that my account is active. I was trying to find an email address for the admins, but I couldn't.

The website does look good though and the discussions on the forum are very good - technical and concise, by a decent group of obviously interested people. Well worth a look if anyone's into the hobby. I've already learned loads from reading old posts over ther last 2 weeks (though I can't post myself).

northdublin

the frequency db site seems to be down at the moment.....not sure why. its a good resource maintained by decent folk.

Taildragon

northdublin wrote: »

... on the dipole idea the thicker you have the wire that you use to construct it the wider the band width will be....ie it will be more resonant over a wider frequency range and if posible use heavy duty coax like rg-213....not the rg-59 light stuff.

watty wrote: »

A little knowlege is dangerous.

At VHF/UHF thicker wire will do what you say and RG213 is better. At CB frequencies, no.

In what way was the offering from northublin dangerous? It is not only innocuous, but completely accurate. The bandwidth of a dipole antenna in free space is directly proportional to the ratio of element diameter to resonant wavelength.

watty

The principle is true, but the lack of knowledge is obvious since the diameter needed for significant bandwidth at HF needs a cage, not a thick wire.

"A little knowledge is dangerous" is a general saying. obvously it is not to be applied literally in this case.

PauloMN

Crazy Ivan wrote: »

When I try these frequencies in the evening/night time, I can't seem to get anything at all and I'm wondering if it has more to do with my set-up. I mean I know it's fairly basic for now, but is it so completely unsuitable that I wouldn't hear a peep? My antenna is obviously grossly lacking. In saying that, I can often hear Hamburg Met RTTY feed on 10.1 MHz with nothing more than this whip. If I mounted an external, or even used an old CB mag mount I have lying around, should I get more of the midland activity? Would a matched long wire be more suitable? Or is there just little to no activity at these frequencies receivable in or around Galway/the west?

In answer to this, I'd say it's a combination of a poor antenna and a lack of activity on those frequencies. The scanner you have is an excellent radio by the way, one of the best general scanners I've used, but to hear really weak HF stuff you'd be better off with a dedicated HF radio.

As regards CB, you need to decide if you want to optimise reception of ground wave signals (in which case you should get something like an Antron 99 and lash it up as high as you possibly can) or whether DX/skip would be of more interest (in which case a properly constructed and matched dipole outside at a reasonable height should suffice).

If you want to get into general HF listening and are investing in a HF receiver, maybe a combination of a general long wire with a tuner and a G5RV for the amateur bands would be a decent combination.

watty

A vertical is allowed for CB, but a dipole can only legally be used for CB reception. The Regulations state that a CB aerial may not be directional.

zilog_jones

Would it be possible to receive any CB on a normal shortwave radio with the built-in aerial? I have an Eton E5 - it lets me tune into all the CB band at least (right up to 29999kHz). Is it all AM over here?

watty

You are allowed AM 1W and FM or SSB 4W. (Actually the same PA, as the carrier on AM must sit at 1/2 max RF voltage , to allow full modulation, which is thus 1/4 power. 1W is thus the no Audio power on AM. The SSB power is actually 4W peak, and typically 2W to 3W RMS with normal audio, and zero power with no audio. FM is 4W no matter what the audio level).
An AM radio will hear FM too via slope detection.

If there is any carrier leakage and signal is strong, then SSB can be received. Another trick for SSB is a second SW radio and tune it to whistle then beat to zero on fine tuning. The L.O. of the second set (typically tuned to a different frequency) acts as a re-injected carrier. Tuning is awkward though.

Psychobiker

Hey!! Is this Watty from www.satellites.co.uk?!

watty

I had to actually think about that.

I have used various UK fora.

I have possibly even used that site.

But a quick search reveals a different "Watty", I have no CAMs, never did and never even claimed anywhere to be in Yorkshire. I've been no closer than Birmingham/Liverpool/London.


The poster below is I'm afraid unconnected. A coincidence of Nicknaming:
http://www.satellites.co.uk/satellite/374118-post1.html

Not a convincing impersonation either. Only 5 posts. If I did want to pirate TV, I'd manage with a bar of chocolate, ballpoint pen spring, raw egg and a pair of tights. (OK I've watched too much McGyver).