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Icom 756PRO2 On 20 Metres tuning light flashes at 2.1 SWR then tuner cuts out and SWR goes to Infinity.All other bands OK. Aerial Butternut HF9V.

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What kind of antenna tuner do you use? (automatic or manual)
Personally I use the LDG AT-7000 and a G5RV. I have absolutely no problems on any frequency.

Posted on Nov 09, 2008

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Posted on Jan 02, 2017

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How does a person adjust the swr with the built in swr calibrator


You can't adjust the SWR with the built in calibrator. The radio has a built in SWR tester but does not have an antenna tuner.
Ideally you should tune or repair the antenna.
Secondly where that is not practical, there are antenna tuners available for sale. Find and buy one and it should correct your C/L imbalances or impedance problems.

Feb 18, 2016 | Radio Communications

Tip

How to Build: Antenna Tuners


Get you a metal box about 4 inches X 4 inches. Use 2 female Cb antenna inputs from old Cb radios or Radio Shack. Get a old Am radio tuner out of a AM radio(530-1700 khz.) Buy or scrap up some copper wire; big gauge I used. Wound 8-10 turns about " 1 inch round close tight wound. Solder to AM tuner- C1 it shall say on top of Am tuner. Solder Center of Am tuner to Ground(Metal box). For those who know electronics the Tuner is 0-365pf Am band 530-1700khz types. OK, back to assembly. drill a hole for the Two Female Cb Inputs on both sides of metal box. Attach copper wire inside to center taps of Inputs on both sides. Drill a hole for Am tuner and Screw on its lock nut and place a knob on it. Solder all grounds of Female Antenna inputs and Tuner Ground and all Grounds to metal box. Use a washer and Bolt to lock down Grounds to Box. This is how it operates after you use a Jumper to hook to TX of Cb radio. Antenna to other side. Its just a simple L/C network. The Tx travels through copper wire(coil) inside box and gets shunted to ground by the right level of PF Capacitance. The operator tunes it in to get a close to 1.1 to 1.5 SWR ratio. Its simple, but helps with bad Antennas.

on Apr 01, 2011 | Radio Communications

1 Answer

Hallo iam using a icom 718 on 28mhz up to 14mhz have a problem of a high swr reading but the antenna is fine then power drop away


Check the feedline to the antenna, and the antenna itself. High SWR means that power is being reflected back from the antenna. A good discussion of SWR may be found here: http://www.hamuniverse.com/wc7iswr.html

If you antenna is designed for 10M and your are trying to transmit 20M on it, there will be a significant mis-match. You may want to look at installing a better broadband antenna, such as an OCFD that will operate better on multiple bands.

Feb 18, 2015 | Icom IC-718 Base radio, HF, 100W

1 Answer

Hannspree TV tuning from aerial problem.


do you mean if you hooked up the tv with the aerial antenna can not get any channel? ok if just a white raster only and doesn't scan or tuned even manually and auto search, the cause is bad tuner.

Sep 06, 2012 | Hannspree Televison & Video

1 Answer

Ihave an old icom icm- 55 marine radio what ariel do i need and do i need to swr the ariel will a cb ariel work basically what do i need to do to get it working


All marine VHF radios must be licensed. A marine radio station must also have a call-sign allocated to the vessel it is installed in. Shore based stations can also be licensed but only where they are involved in marine based activities e.g Yacht Clubs, Marinas, Harbour Masters, Rescue Services etc.
In the UK ships radio licences can be obtained from Ofcom. They are free for non-commercial users.
The user must also have a Marine VHF Radio operators certificate. This requires taking an exam. In the UK contact the Royal Yachting Association for a copy of the syllabus and local examiners.
More information about the licensing rules, courses and exams can be found here. http://www.rya.org.uk/infoadvice/regssafety/Pages/licensingelec.aspx
The ICOM ICM55 is a good radio set and can still be used in an existing (marine) installation but it does not meet the standards for new installations as it does not have DSC (digital selective calling) capabilities - which all new fixed sets must now have. It is therefore very unlikely that you will be able to get a licence to install one.
To get it working you will need a proper marine band VHF aerial which operates in the frequency range 156-MHz. They usually come with cable attached but if a longer cable is needed, or the aerial is not cabled in the first place, use flexible 75 ohm co-axial cable with a copper core and braid/foil screen. Use proper aerial connectors (type F or BC are most commonly used and can be obtained from most good electronic component suppliers more cheaply than from a boat chandlers. Do not use push-fit TV aerial plugs)
Citizens Band radio works on the much lower frequency MHz band and therefore a CB aerial will not work with a marine VHF radio set. Please see this Wikipedia article for more information http://en.wikipedia.org/wiki/Marine_VHF_radio

Jan 28, 2011 | ICOM Informatique IC-F420-55 UHF...

2 Answers

Got it peaked and tuned and hooked up a new coax and mirror bracket and my swr is at 4. Before I did all this I had the stock coax and swr was under 2. What do I need to do to get the swr down?


The antenna needs to be tuned. The reason all of a sudden your SWR is a 4 when it used to be a 2 is, after a peak and tune, the radio is putting out more power, there for more RF energy is being reflected back into the radio. That is why the antenna has to be tuned.

It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.

Nov 17, 2010 | Cobra 29 LTD CB Radio

1 Answer

I've got a Cobra 29 with WX and BT, the antenna light comes on, the swr meter barely moves and it doesn't seem to send or receive, still gets weather. May have been run with a bad antenna, got a new...


Please make sure you are tuning the antenna correctly.



It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.






Now: If you have adjusted the antenna properly and you still get the antenna warning light, then the antenna warning circuit may be out of whack. Use an external SWR meter.

You may also be getting common mode current. Its when RF comes down the outside of the coax. If the swr goes up with modulation then it's common mode.

Here is how to stop common mode.

As close to the antenna as you can while still inside the vehicle, take about 6 to 8 inches of the coax, and coil it up into tight even coils and secure into shape with electrical tape.

This is an RF choke, and will stop the common mode current.

If all other radio's are fine and no ant light come one, and are all showing low swr, then turn VR6 back to disable the ant warning light. "only do this if the ant light comes on when SWR is lower then 1.5 and does not swing up with modulation showing that the ant warning light is miss aligned.

Nov 07, 2010 | Cobra 29 LTD CB Radio

1 Answer

If i use 2 18 ft. cables, will this help to bring swr down


No. Coax length will not change your SWR, however it may trick the meter. (not usually). Your SWR problem is with your antenna.

With 2 18ft lengths you will make the antenna more broad band, but your SWR will be the same.

Here is a list of SWR problems and solutions.

Here is how to tune an antenna.

Hope this helps.

Oct 20, 2009 | Cobra 29 LTD CB Radio

3 Answers

What antenna would you recommend for my cb? cobra 29ltd


depends on what vehicle its going on. If its a car, you don't need anything crazy, unless you are going to run a linear.

You are fine with a wilson 500/1000 mag mount or a k40 mag mount.

just make sure you tune the antenna for lowest SWR.

Sep 29, 2009 | Cobra 29 LTD CB Radio

2 Answers

SWR Meter


No problem, Follow the link http://support.radioshack.com/productinfo/DocumentResults.asp?sku_id=21-525&Name=CB%20Accessories&Reuse=N It's off to the right under other documents. Good Luck and hope this helps L8R

Sep 17, 2007 | Panasonic CR-SRF100 SIRIUS Radio Receiver

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