SWR Readings are bugging me

[338_MtRushmore]

So I installed a new 2950dx, a puck mount and a monkey made antenna in my 2005 Ram. This replaced a Stryker 955hpc, a firestick stud mount and an Everhardt Master Blaster 2. I never had an issue with swr with the Stryker. I used the same coax (pro58au/95) except I soldered the rings instead of crimped like before, and I wound 5 turns on 4.25" of air. With a Radio Shack meter, I get 1.2 to 1.5 (1 and 40) with a 6' rg8x, and the radio only shows 3 bars for swr. With both a 2' cheap crimped coax and a 6' soldered coax (the clear truck stop type) it pegs the meter and the radio meter. If I plug the antenna straight to the radio, it pegs the radio's meter. I have checked continuity and everything checks out, but there must be something going on. I am planning to run rg8x with the same choke and see what it does, as there were some pretty tight bends in the existing coax. I also should be getting a rigexpert aa-30 in the mail tomorrow, and I hope that will shed some light. If the analyzer says the swr is good, would you still check it with a meter, or just call it good?

 

[Bearcat]

Hmm...could be the solder joint..or coax

 

[Bearcat]

Check with analyzer..and meter..check and double check..think of the simple stuff first from antenna back

 

[Mudfoot]

Must be a cable or connector issue.

 

[338_MtRushmore]

I guess I don't understand how it can read good with the meter and 1 jumper, but not with other jumpers or straight to the radio. Hopefully the analyzer will tell the tale

 

[Mudfoot]

Looks like a decent analyzer.

 

[338_MtRushmore]

After playing with the analyzer for a few minutes, it looks like the swr meter in the 2950 goes full scale around 1.6:1. Now I just need to figure out how to effectively use this tuner. Maybe now that I have a tuner, i can actually tune a homemade antenna. Every prior attempt ended in frustration.

 

[M0GVZ]

After playing with the analyzer for a few minutes, it looks like the swr meter in the 2950 goes full scale around 1.6:1. Now I just need to figure out how to effectively use this tuner. Maybe now that I have a tuner, i can actually tune a homemade antenna. Every prior attempt ended in frustration.

Sweep at least 1-2MHz either side of where the antenna was designed to be tuned for. When you use a very good ground the antenna usually ends up being too long as standard and you can easily find its lowest SWR is below the CB frequencies by a couple of hundred MHZ, that's why an antenna analyser is a godsend as it allows you to measure outside of where your radio will transmit.

The 234/f formula for making a 1/4 wave antenna if that's what you used is merely a starting point, not where the end result usually ends up being.

 

[338_MtRushmore]

Sweep at least 1-2MHz either side of where the antenna was designed to be tuned for. When you use a very good ground the antenna usually ends up being too long as standard and you can easily find its lowest SWR is below the CB frequencies by a couple of hundred MHZ, that's why an antenna analyser is a godsend as it allows you to measure outside of where your radio will transmit.

The 234/f formula for making a 1/4 wave antenna if that's what you used is merely a starting point, not where the end result usually ends up being.

I cut 5/8" off the whip and the resonance point moved from 26345 to 26550. I am going to swap the coax and finish bonding before I get too carried away tuning this. Thanks for your help on bonding, it definitely makes a difference.

 

[M0GVZ]

I cut 5/8" off the whip and the resonance point moved from 26345 to 26550. I am going to swap the coax and finish bonding before I get too carried away tuning this. Thanks for your help on bonding, it definitely makes a difference.

Definitely finish the bonding before doing a final tune. You'll know when you've done enough bonding because the resonant point of the antenna will stop falling. Doing the exhaust won't alter the antenna resonant point but is done to reduce interference because the exhaust makes a good antenna for engine made RFI. If you've still got ignition or alternator noise try a nice fat strap from the engine block/head to the firewall.

It would be nice if you could keep a record of just how much your antenna's tuning point shifted by and/or how much you ended up shortening it by and posted about it, maybe starting a fresh thread about the installation just to demonstrate to others how doing it this way can make a difference.

 

[222DBFL]

Great ideas there M0GVZ. It helps others a lot when someone does this. If it's not too much trouble that is!! And it's good for your records. Let's you know how good of a job you've done. And I'm 110% with M0GVZ about the tuning of the antenna. Complete all bonding and the install before you tune antenna. If possible try to get a reading at the antenna feed point and at the radio end of the coax. Things can change from point a to b. I'm sure you already know this, but just in case. Keep up the good work. It will be worth it in the end of you are trying to achieve the best you can!!!

 

[338_MtRushmore]

Great ideas there M0GVZ. It helps others a lot when someone does this. If it's not too much trouble that is!! And it's good for your records. Let's you know how good of a job you've done. And I'm 110% with M0GVZ about the tuning of the antenna. Complete all bonding and the install before you tune antenna. If possible try to get a reading at the antenna feed point and at the radio end of the coax. Things can change from point a to b. I'm sure you already know this, but just in case. Keep up the good work. It will be worth it in the end of you are trying to achieve the best you can!!!

I was never planning to measure at the feed point. The puck is mounted about 6 inches behind the dome light, and there is a 2 inch tail coming off the choke that has ring terminals for the puck. Right now I pretty much have to remove the 4 rear door pillars and drop the headliner to access the feed point. Any Idea what the best method of doing this might be? I could run a short coax to the dome light?

 

[222DBFL]

Yes a short coax will be fine. As close to feed point as possible. 3ft. Is fine. And when you add your coax run to the radio make sure the readings stay the same. The dummy load is just to give you a base line of what your MFJ meter shows with a near to prefect match, which in this case is the 50 ohm dummy load. Take down the numbers that show with the dummy load connected directly to the MFJ meter and use this as your base line for final tuning of antenna. Keep up the good work and it will pay off!! Good evening.

 

[rabbiporkchop]

I was never planning to measure at the feed point. The puck is mounted about 6 inches behind the dome light, and there is a 2 inch tail coming off the choke that has ring terminals for the puck. Right now I pretty much have to remove the 4 rear door pillars and drop the headliner to access the feed point. Any Idea what the best method of doing this might be? I could run a short coax to the dome light?

If you had used a half wavelength of cable from the feed point to your radio your measurements would be identical at the feed point and at the end of the cable but using any length of cable other than a multiple of half-wavelength will give you impedance changes at both ends of the cable.

 

[338_MtRushmore]

I doubt I will be posting any results, because my radio was stolen today along with my antenna, analyzer and truck.