27Mhz finally installed

Submitted: Tuesday, Jan 04, 2005 at 19:31
ThreadID: 19068 Views:1686 Replies:4 FollowUps:4
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Hi All

Some of you may remember my post asking if i should install the 27Mhz GME TX 830 into my car.....some said yes some said no.
Just a few more questions and i appoligise if they are strange or obvious:)
Well i went to Dick Smiths and bought a complete aerial kit ($37.50) which seems to be the type that you cant adjust and was wondering if it would be better to spend a little more money on the ones you can adjust yourself?....would i get a better range and if not how would i?.....im guessing you will all say buy a AM/SSB unit with USB/LSB.
Also being so long since i have owned a CB im a bit stuck with what to do with the "RF gain" on it. When i try and talk should it be adjusted so that the LED bars are on red all the time or should it be middle around green or lower etc?
And last the "ISC" switch.....never heard of that before.....should it be left ON all the time or switched OFF.....again im sorry for all the questions......i will get a UHF rig oneday but for now this will have to do.
Thankyou all in advance.


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Reply By: AussieChris - Tuesday, Jan 04, 2005 at 19:37

Tuesday, Jan 04, 2005 at 19:37
Just downloaded the manual for it online and have seen that the "ISC" button if for excessive noise and from memory 27Mhz CB's had excessive noise anyway so wouldnt hurt to have it on i guess:)
Forgot one other question......along with the Aerial i bought a "Boot Mount" bracket with it......all i did to attach the aerial was screw the mount onto the underneath of the boot and attach the aerial......is that all you do?


AnswerID: 91313

Reply By: Savvas - Tuesday, Jan 04, 2005 at 20:27

Tuesday, Jan 04, 2005 at 20:27
This is going back a bit. I used to use a Pearce-Simpson 27Mhz AM/SSB unit a long time ago. Around 1988, in fact. I still have it sitting around somewhere.

With the boot lid mount, you attach the aerial base to the mount and then clamp the mount to the boot lid using the screws. It would be a good idea to get a solid pice of rubber between the screws and the boot lid to stop the screws cutting through the paint. Personally, I think the Z bracket mounted next to the bonnet is a better solution.

I found the antennas with the adjustable tip to be worthwhile. If you get a bit over ambitious tuning the other type by removing too much wire while tuning it, then there is no going back. With the adjustable type, you just lengthen or shorten the tip without worrying. With either antenna you will need a SWR meter between the radio and antenna to get the tuning right, unless your unit has a built in SWR meter.

Select Ch40, press the mic button to transmit and take a reading with the SWR meter. write the number down. Now select Ch1, repeat the procedure and record the reading. Ideally, the reading should equal 1:1 throughout the frequency range. However sometimes the best you can get is just to have the reading equal across the range but it must be less than 2:1 and preferably less than 1.5:1. Higher than 2:1 can damage the radio.

If the reading is higher on the higher channel, the antenna is too long and must be shortened. If the reading is higher on the lower channel, the antenna is too short and must be lengthened. An antenna without a tunable tip can't be lengthened.

Good luck!
AnswerID: 91323

Follow Up By: AussieChris - Tuesday, Jan 04, 2005 at 20:37

Tuesday, Jan 04, 2005 at 20:37
Hi Savvas

Thanks for your info......i will find out how much a adjustable aerial is this week and see if it makes a difference.
you seem to have got yours around the same time i got my first CB mind you it didnt have SSB was just a stock standard AM CB then i managed to find a USB/LSB unit which i loved to death. (pitty they still arent as popular.
Im sure since setting mine up this arvo i have heard a "Very Faint" crackle of voices on CH 8 but maybe it is just me "Hoping" that i hear something after all these years.....lol.
Guess i will have to keep trying a few things to get the signal stronger and see how i go.

thanks again

FollowupID: 349878

Reply By: ozzyark - Tuesday, Jan 04, 2005 at 22:23

Tuesday, Jan 04, 2005 at 22:23
Hi Chris,
Good to see you got it up and running okay.
Did you get hold of a SWR meter? Because if the SWR is too high it will affect the sort of reception you get. As for the ISC switch you would have to check that leaving it on isnt going to block out any faint stations as some of the noise limiters seem to do.
As for your antenae, if you get around to checking (what type of aerial is it?) the swr on the new antenae its a good idea if you tune it in on ch20 middle ground, that way it is about even on all channels. If it is a black helical type aerial you just have to grab a pair of snips and take of the pretty little red hat on the end and snip a very small piece of the end, recheck the swr if it has come down a bit snip a little more and so on till you get it down to about 1.5:1. If by accident you snip too much off we use to just unwind a bit of the wire used on the antenae and add a bit back on. In fact we use to wind our own antenaes, gettiing them smaller and smaller.
I actually put my AM rig in my camper this morning, just have to check the antenae tommorow I ended up puting mine on the bullbar so it will be interesting to see what the SWR says.
Cheers for now
AnswerID: 91346

Follow Up By: AussieChris - Wednesday, Jan 05, 2005 at 10:34

Wednesday, Jan 05, 2005 at 10:34
Hi Ozzyark

Didnt get hold of a SWR meter so might have to maybe take it to a communications mob in town here and get them to check it for me?
The aerial i bought was just a standard 27Mhz helical type so no tips to adjust.
I will see what this one reads and will go from there......also does anyone know what the LED bars should be on when i transmit and recieve (If i ever recieve...lol).....if i adjust the RF gain as i talk the LEDS go up so should they be on full red all the time? is there a way to adjust them correctly.

Cheers guys

FollowupID: 349958

Follow Up By: KiwiAngler - Wednesday, Jan 05, 2005 at 14:44

Wednesday, Jan 05, 2005 at 14:44
SWR is important but it affects transmission not reception.

SWR (sometimes referred to as Standing Wave Ratio) should be 1:1 in simple terms that means that for every watt you transmit from the radio 1 watt then leaves the aerial. If you do not have a 1:1 (or as close as possible) you will not get the transmit coverage that you ideally could and if the SWR is REALLY off then you run the risk of blowing the radios transmitter. This happens almost instantaneously if you ransmitt without an aerial because the SWR is 1:0 or simply put the radio is trying to put out 1,5,20 watts of power and it has nowhere to go so it just blkows the transmitter. So the closer to a 1:1 SWR ratio you get the better the TRANSMISSIONS will be. You can actually RECEIVE radio signals on almost any sort of aerial its the TRANSMITTING on aerials at least than 1:1 SWR that causes the problems.
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FollowupID: 349996

Reply By: AussieChris - Wednesday, Jan 05, 2005 at 21:51

Wednesday, Jan 05, 2005 at 21:51
Hi KiwiAngler

If the aerial i have is a tuneless one do i just take it that all will be ok????
As Ozzyark said i can just take the little red tip off it and snip little by little off until its ok but i thought these aerials were tuned in automatically so you wouldnt have to worry about the fuss

AnswerID: 91500

Follow Up By: AussieChris - Wednesday, Jan 05, 2005 at 22:12

Wednesday, Jan 05, 2005 at 22:12
Also would plugging an AM CB into a UHF aerial damage the unit at all?
Silly me plugged it in to a mates UHF aerial not even thinking......worst is i not only plugged one unit in but both units that were same make and model etc so now im not sure if either of them are working properly or not.....also if the SWR is out and it blew the transmitter would i even know its blown? .

FollowupID: 350071

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