SWR major problem

[CyberWarrior]

I have a Falcon dipole,stretched across to a tree and a hook on the side of trailer.No matter what I do,it stays on this meter on the red side: 4 : 1 over all chanes

also does anyone know,how to ground a dipole ???

 

[NDRADIONUT]

How long is each side ?

 

[sloop]

No a dipole doesn't have to be grounded, however it is advisable to make sure you have lightning protection on the coax. On a dipole one side is connected to the inner conductor of the coax (hot side) while the other side is connected to the outer shield of the coax (ground side). From one end to the other should be 1 wave length of your signal. For 27 mHz (CB) that would be approx. 11 meters long (~36 feet) with the 'null point' (center of the transmitted wave) being the feed point of the coax. Living in a mobile home you will get better results if you 'hang' the 'ground' end of the antenna at the mobile home and the 'hot' end at the tree. Google 'dipole antennas' to find out the many different ways the dipole can be hung. Good luck.

 

[jwt873]

I wasn't familiar with the Falcon dipole, so I took a look on Google..

It looks like a good unit with a molded center connector and insulators included for the ends. I don't see any easy way to 'tune' it. Usually when you install a dipole, you need to adjust the length by a few inches to get the SWR down to an acceptable level. This one seems to be pre-cut and not easy to trim. Were there any tuning instructions included with the kit?

I'd look at the coaxial cable first. Make sure that you have continuity between each of the center pins and each of the outside rings of your PL-259 plugs. Also make sure there is no resistance or a short circuit between the center pin and outside ring.

If your coax is fine, then it's an antenna issue.

You'll have to find out where it's resonant. If you're in the red on all channels, then you'll need an antenna analyzer to find which frequency has the lowest SWR. If the minimum SWR is at a frequency lower than the citizen's band channels, then you'll have to shorten the overall antenna length. If it's low at a frequency higher than the CB channels, then you'll have to lengthen it by soldering extra wire on the ends.

 

[prcguy]

A dipole antenna is not a full wavelength long, its 1/2 wavelength overall and each element is 1/4 wavelength long. That would leave you with a total length of about 17 1/2 ft or 8ft 9in each element.

Making a dipole a full wavelength would leave each element a half wavelength long and the feedpoint would be a difficult or impossible match to coax being several thousand ohms and the radiation pattern would have four lobes like a clover leaf.

A dipole also radiates symmetrically because there is equal RF currents flowing in each element, so there is no hot side or ground side when it comes to radiating a signal. Either end can be in the tree and there will be no difference in performance if you swap them.

The Falcon brand dipole should have been pre tuned so you either have it mounted too close to or touching a large metal object like a trailer or your coax has a problem. If its any closer than a few feet to the trailer move it away and check the match or swap out the coax, Otherwise there is not much to go wrong unless its length has been changed.
prcguy

No a dipole doesn't have to be grounded, however it is advisable to make sure you have lightning protection on the coax. On a dipole one side is connected to the inner conductor of the coax (hot side) while the other side is connected to the outer shield of the coax (ground side). From one end to the other should be 1 wave length of your signal. For 27 mHz (CB) that would be approx. 11 meters long (~36 feet) with the 'null point' (center of the transmitted wave) being the feed point of the coax. Living in a mobile home you will get better results if you 'hang' the 'ground' end of the antenna at the mobile home and the 'hot' end at the tree. Google 'dipole antennas' to find out the many different ways the dipole can be hung. Good luck.

 

[rfradioconsult]

Your problem may be how you are running your coax away from the center of your dipole, ideally you want it to leave the antenna at 90 degrees from the antenna and not parallel to the antenna. If you need to add extra coax to route it away from the antenna that would be ok.

 

[Retroradio]

Radio or external SWR meter? That could make a differecne as well.

 

[CyberWarrior]

How long is each side ?

Ok the radials measure roughly 92 inches,from tip to center connector

 

[CyberWarrior]

Radio or external SWR meter? That could make a differecne as well.

I measured with built in bridge,also used a PDC7 external. Both these meters show 1:1

The other meter I used is a Workman HP201S,this one shows 4 : 1 all across the band.

 

[CyberWarrior]

Your problem may be how you are running your coax away from the center of your dipole, ideally you want it to leave the antenna at 90 degrees from the antenna and not parallel to the antenna. If you need to add extra coax to route it away from the antenna that would be ok.

The way I have it is: T layout.

 

[CyberWarrior]

I wasn't familiar with the Falcon dipole, so I took a look on Google..

It looks like a good unit with a molded center connector and insulators included for the ends. I don't see any easy way to 'tune' it. Usually when you install a dipole, you need to adjust the length by a few inches to get the SWR down to an acceptable level. This one seems to be pre-cut and not easy to trim. Were there any tuning instructions included with the kit?

I'd look at the coaxial cable first. Make sure that you have continuity between each of the center pins and each of the outside rings of your PL-259 plugs. Also make sure there is no resistance or a short circuit between the center pin and outside ring.

If your coax is fine, then it's an antenna issue.

You'll have to find out where it's resonant. If you're in the red on all channels, then you'll need an antenna analyzer to find which frequency has the lowest SWR. If the minimum SWR is at a frequency lower than the citizen's band channels, then you'll have to shorten the overall antenna length. If it's low at a frequency higher than the CB channels, then you'll have to lengthen it by soldering extra wire on the ends.

No unfortunately,no documentation came with it.

 

[NDRADIONUT]

Cb band should be 102" on each side...

 

[jwt873]

I measured with built in bridge,also used a PDC7 external. Both these meters show 1:1

The other meter I used is a Workman HP201S,this one shows 4 : 1 all across the band.

If the meter in the radio and the PDC7 both show a 1:1 SWR, I'd suspect that the Workman meter might not be that accurate.

The most important thing is that the radio is happy with the antenna. That would be good enough for me.

The only other option you have is to get yet another SWR meter and see what it says.

 

[prcguy]

Sounds like your dipole is probably fine and one meter is crap. You can test the SWR meter using two 50ohm loads and a T adapter. You should get a perfect 1:1 match with one 50 ohm load on the antenna port of the meter and if you use a T adapter and two 50 ohm loads (25 ohm total) the meter should read exactly 2:1. If not toss the meter in the trash.
prcguy

I measured with built in bridge,also used a PDC7 external. Both these meters show 1:1

The other meter I used is a Workman HP201S,this one shows 4 : 1 all across the band.

 

[CyberWarrior]

Here is the dipole I put up today,same thing 4 : 1 all across band.
Uniden says 1: 1



Full Wave Base Station Dipole Antenna CB Radio Band Citizens Band 11 Meters | eBay

 

[NDRADIONUT]

Cb band should be 102" on each side...

 

[CyberWarrior]

Yes that would equal 1/4 wave or 9 feet.
I posted the wrong model from EBay but,you get the idea.
I did diag on the antenna system and now,instead of showing pass I get fail.
I'm very close on taking the radio,sell it anddump both dipoles and just give up.

One thing: Does coax age,affect swr? If so,then I have my answer,if memory serves me,this coax is 40 yrs old,very well taken care off but.....

 

[jwt873]

Coax can degrade.. Especially after 40 years. Coax Attenuation | Coax Cable Loss | Radio-Electronics.Com However I doubt if age would account for a 4:1 ratio.

But I'm curious as to why you believe the Workman meter, but not the meter in your radio or the Astatic meter?

 

[Retroradio]

Coax can degenerate with age\use.

 

[NDRADIONUT]

The connectors may not be too great either if they have been on there for the same 40 years...