AM CB Radio - 27MHz

Submitted: Monday, Jun 20, 2016 at 20:30
ThreadID: 132825 Views:3052 Replies:7 FollowUps:5
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Greetings,
I have a standard run of the mill 80 channel UHF CB fitted to my vehicle with a 6.5 db aerial on a standard base. I am curious to know if I can connect an AM 27 MHz aerial to the same base and then connect the other end of the aerial cable to my old AM Uniden PC122XL and expect it to work or do I need to get a separate 27MHz base and run a separate cable to connect to my old CB. Would it cause any damage to my old CB?
I'm simply curious to see if there's anybody out there who still transmits on the old 27Mhz frequencies. I'm also interested to know if there is anyone using the old SSB.
Thanks
WBS
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Reply By: Member - eighty matey - Monday, Jun 20, 2016 at 21:14

Monday, Jun 20, 2016 at 21:14
G'day WBS.

I have an AM/SSB 27 Mhz in the Land Cruiser. I just ran separate cable and aerial from Jaycar for less than $50. I just about certain you have to use the specific lead and aerial.
There's not much on there. Up we're getting a bit of Asia talking but I reckon it could be a bit of a back up if all else fails.

I might hear you one night but we're in the NT for a while.

Who knows what the call channels are and what the way to call?

Hoo roo,
Steve
AnswerID: 601667

Follow Up By: Stu & "Bob" - Wednesday, Jun 22, 2016 at 21:44

Wednesday, Jun 22, 2016 at 21:44
G'day Steve,
As I remember, the call channels are/were 11 AM, 16 & 35 LSB.

I still use 27MHz from time to time, but only SSB via my Codan.

Regards
Stu
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Reply By: Member - Stephen L (Clare SA) - Monday, Jun 20, 2016 at 21:21

Monday, Jun 20, 2016 at 21:21
Hi WBS

The problem is not the base, but the antenna. If you do not know, UHF and the old AM radios are very different. Your stock standard UHF antenna you connect to your UHF off the shelf is pre tune and nothing more to do. The AM on the other hand must use a 27 meg antenna, and then you must tune the antenna to your radio, only trimming very small amounts off the antenna at a time.



All the best



Stephen

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AnswerID: 601668

Follow Up By: Member - Boobook - Monday, Jun 20, 2016 at 21:53

Monday, Jun 20, 2016 at 21:53
Yes, that's is referred to as SWR, I would also add that a 27Mhz needs a good ground plane and many UHF antennas don't so the mount is probably very different.

You may also need to get the right length cable.

It is best to have 2 setups.

If you need 1 then get the 27mhz one professionally installed and tested and use that for UHF with the right antenna.
2
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Reply By: vk1dx - Monday, Jun 20, 2016 at 21:57

Monday, Jun 20, 2016 at 21:57
It will work if you change the anenna and radio to the 27Mhz ones. But it may not be a good system. In an emergency okay, but not for serious chit chat.

Phil
AnswerID: 601671

Reply By: maurice b - Monday, Jun 20, 2016 at 23:02

Monday, Jun 20, 2016 at 23:02
Yes you can use your uhf lead and balum to operate your 27 mhz radio with a 27 mhz Antenna . 27mhz antenna's come pretuned to a working swr for all channels.Back in the 70/80's we use to CQDX to many overseas countries . When you made a contact you would exchange postal address then recieve a QXL card in the mail from that contact.This was with the sets with upper and lower side bands pushing 15 watts . We used a SWR meter to adjust antenna lenght for optimum transmission
AnswerID: 601674

Reply By: Member - WBS - Monday, Jun 20, 2016 at 23:30

Monday, Jun 20, 2016 at 23:30
Thanks for the replies.
I found my old AM CB radio in a cupboard in my garage the other week. It was a good unit but wasn't used for too long before UHF came in and took over so it was put away. I thought I might resurrect it for old times sake and give it a try but didn't want to run a new base and cable just for that.
I was aware that the UHF aerial wouldn't work but I was just curious if I fitted my old AM aerial of which I have a couple to the exisiting mount, could I use the same base and the same connector on the CB end. I might give it a try.
WBS
AnswerID: 601676

Follow Up By: Robin Miller - Tuesday, Jun 21, 2016 at 09:38

Tuesday, Jun 21, 2016 at 09:38
It will work, we use 27mhz SSB as it has more range in general and a lot better in the Vic high country. PC122 is SSB & AM.

Because its fallen into disuse with little traffic its effectively a private channel.

Still a bit of traffic on call channel 35 ,but its ssb not much AM.
Robin Miller

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Follow Up By: Member - Boobook - Tuesday, Jun 21, 2016 at 13:51

Tuesday, Jun 21, 2016 at 13:51
Robin, is that traffic on channel 35 on LSB?
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Follow Up By: Robin Miller - Tuesday, Jun 21, 2016 at 15:55

Tuesday, Jun 21, 2016 at 15:55
Yep lsb as per Old mate.

We use channel 16 mostly and also have it on my HF (backup) as well as my 4 remaining PC122s.

The PC122 and SSB have quite interesting characteristics that make them quite useful over UHF.

Its has an RF gain control and I wind back the gain (as opposed to a mute).
This means that it ticks along quietly in the background and because of the nature of SSB you can hear others in the background and voices don't get locked out as they do with F.M. (sort of like when out with a group for dinner you can tune into 1 voice over the others).

When in a convoy I try to have 27nhz at front and rear and with better range can have a conversation outside of the trips UHF chatter.
Robin Miller

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Reply By: old mate - Tuesday, Jun 21, 2016 at 15:45

Tuesday, Jun 21, 2016 at 15:45
I run an old Pearce Simpson Super Panther Mk1 in my work Hilux in SW QLD.
6FT helical antenna on the roof. At present there is a lot of skip late in the afternoon. At the moment a lot of NSW and Vic stations around. When the conditions are good I can hit NSW, WA and NZ from here. I do hear stateside but I cant reach them.

Yes its on 35 LSB but it often gets used a chit chat channel not people calling CQ-DX to initiate long distance contact. I have heard of some clubs and caravanner groups using AM CB so they don't get all the "traffic" on UHF but I don't bother with it, but then I'm a long way from nowhere.
AnswerID: 601695

Reply By: Echucan Bob - Wednesday, Jun 22, 2016 at 23:43

Wednesday, Jun 22, 2016 at 23:43
WBS,
27 MHz is mostly used by enthusiasts and not much by travellers needing comms. Many operators are using 100 watts or more, and reverb effects. There is quite a market for modified radios. CB radio

I can remember talking to stations in the US with an unmodified Uniden CB radio in the 80's.

It's much more fun than UHF but not as useful for talk over a short range. The coax connector, cable and base are the same as your UHF radio, just screw on a 27 MHz whip.

Bob
AnswerID: 601740

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