FFR landy aerials useable for CB?

[tankmaniac]

Does anyone know if the standard FFR copper aerials, approx 9ft, are usable for a CB?

I have a SWR tuner and could tune the aerial if it was suitable.

If not, can anyone recommend an aerial for CB?

I can use my wing mounts on the wings to mount it... but does it need to be touching the metal to ground?

cheers

[Lord Burley]

I had a CB connected up to the FFR ariels on my old LTWT.Worked a treat.

[Tony B]

The mounts are usable. A radio ariel is tuned as a ratio of the wavelength. most civil CB ariels are shorter because of windings in them, the length is coiled. If you don't want to chop about military kit use a length of thin rod, also let you get the length right.

[AlienFTM]

A mate in 15/19H, when CB became the latest must-have (I didn't - I was a Control Signaller and saw enough radios during the day) about 1980, a mate fitted one to his car. I remember thinking what a low frequency German CB must use because his antenna was enormous, so much so that when he drove into the underground car park in downtown Paderborn, it got a serious smack on the lintel.

 

I am sure the citizens' band has changed over time and moved to VHF. I do remember that German CB was illegal in the UK and vice versa (different bands for one thing) and at the ports it became a game trying not to get your CB confiscated.

 

As for the OP's rods. If the antenna is made up of three sections, it is Clansman and the length is three metres (for Clansman HF). If it is composed of two rods, it is Larkspur and the length is 8' (for Larkspur VHF).

[Paul101Clark]

Two whip sections work well with CB radios

[tankmaniac]

thanks for the replies.

changed the aerial, mount and cable and still not got a good signa.

Does the CB chassis have to be earthed too? i mean the CB negative power goes to the battery negative which goes to ground.

My SWR test was a little better although not so good on thevery high channels.

Reference test showing 3 now which is closer to the ideal 1.5.

I have earthed the aerial mount to the chassis.

CB signal is still very low on the scale.

Argh!

[tankmaniac]

Thanks all/.

Do any of you know where i can source connectors and cable?

i could do with making up some BNC to CB cables but the connecs would need to be the pukka ones.

Also, still struggling to get a signal even though i have earthed my base mount and changed the aerial!

does the cb body need to be grounded even though the CB negative goes to the batt which grounds?

[fv1609]

Always a good principle where RF is concerned to bond equipment directly to earth.

 

On receive generally it will make ignition interference less likely to be picked up into the receiver through the coax.

 

If you don't bond the rig to earth on transmit you may experience a voltage drop across the power leads reducing RF power out a little. By bonding to earth then you only have the voltage drop in the +ve lead.

 

From an RF point of view on transmit the rig needs to go straight to earth & otherwise the rig is "floating" above earth & the -ve lead is having to perform an RF function rather than a purely DC role.

 

I think you need to try to tune the whip into resonance. That will improve reception & transmission no end. On 28Mhz I used to use an Aerial Tuning Unit No 8 which was intended for matching a B47 into an 8ft whip. You can use a No.6 which was intended for a C42. The only difference is the resistor in the RF sniffer is higher in the No.6 (27k) than the No.8 (4.7k) as the C42 was more powerful.

 

Before everyone starts frothing at the mouth I should explain you need to detune the ATUs to operate below its lower design frequency which I think was 36Mhz. What I did was to get inside the box & put 50pf trimmer condensers across the matching variable condenser (C8) & the ganged tuning condensers (C9).

 

You can get adaptors for BNC to PL259 (plug or S0239 socket) used on CBs, although these used to be called UHF type, which is an appalling misnomer. In fact inter-series connector kits allow you to mate C, N, BNC & 259 series together. What you have to watch is that 75 ohm BNC has a smaller pin than 50 ohm BNC. If you mix them there is a mismatch, but more importantly a 50 ohm plug into a 75 ohm socket can split the centre connector of the socket. I think the Army system was 75 ohms.

 

G4MBS

Edited January 17, 2009 by fv1609

[Tony B]

Thanks all/.

Do any of you know where i can source connectors and cable?

i could do with making up some BNC to CB cables but the connecs would need to be the pukka ones.

Also, still struggling to get a signal even though i have earthed my base mount and changed the aerial!

does the cb body need to be grounded even though the CB negative goes to the batt which grounds?

 

Maplin's do all the various connectors etc.

[tankmaniac]

Hey nice one.

loads of good information there.

Beleive it or not i got a signal... halfway up the readout as i was up the hill.

came home and signal dropped to 1.7 but was still receiving the signal.

this was great news... until i tried to transmit..

this was the only thing that was working! nada. zilch.

like 1 instead of 30!

must be something dodgy... perhaps my 12v supply connections... will check.

 

Went over the military chassis i have and grabbed a spare 90 degree bnc which is reusable. putting this onto the coax with p259 cb connect to see what the side aerials will do when tuned.

 

i can see a garden style horizintal antennae coming up!

 

Anyone tried these? like 17 or 36 feet long?

[84KB11]

If you are using the metal "tuning ring" under the rubber antenna mount, take the mount off and bypass the small RF matching transformer that is between the BNC and lead to the antenna mount.

I did this on mine and it improved the TX/RX greatly.