Uniden Washington Base Station

[Capt. Kirk]

A little personal background first. I used CB's in my 30's when I was a trucker and now 30 years later I'm jumping back in. Never was a technician...just a user. Recently put a cb in my jeep and set up a base station a few months ago. Anyway, last week I purchased a Washington base station which I was able to briefly talk with my wife out in the jeep yesterday. I'd like to tinker with this so I can learn some things and I'm hoping folks here won't mind some really novice questions. I have an SWR meter and both my Cobra and Washington are 0 or very close to that.
My first question. I see in the operators manual for the Uniden that it wants 52 ohm for the antenna and the best I can gather my Solarcon A-99 is 50 ohm. Does this matter and, if so, what can I do about it? I don't want to do anything to the antenna since I'm sure my Cobra is wanting 50 ohm. Thanks!

 

[AmericanEagle575]

A little personal background first. I used CB's in my 30's when I was a trucker and now 30 years later I'm jumping back in. Never was a technician...just a user. Recently put a cb in my jeep and set up a base station a few months ago. Anyway, last week I purchased a Washington base station which I was able to briefly talk with my wife out in the jeep yesterday. I'd like to tinker with this so I can learn some things and I'm hoping folks here won't mind some really novice questions. I have an SWR meter and both my Cobra and Washington are 0 or very close to that.
My first question. I see in the operators manual for the Uniden that it wants 52 ohm for the antenna and the best I can gather my Solarcon A-99 is 50 ohm. Does this matter and, if so, what can I do about it? I don't want to do anything to the antenna since I'm sure my Cobra is wanting 50 ohm. Thanks!

Welcome to the Group, feel free to ask any questions about radio,etc..great bunch of People in this group who would be happy to help you out, again welcome!!
73's

WDX 1863
Steve

 

[Brother DXer]

Welcome to the forum, Capt. Kirk
Steve is right, there are definitely some very knowledgeable people here and most will help with questions you may have.

As for your Washington, I don't know this for fact, but there shouldn't be any issues running this on your 50 ohm antenna.
I'm sure someone who actually knows, and can explain it, will chime in.

 

[Capt. Kirk]

Welcome to the forum, Capt. Kirk
Steve is right, there are definitely some very knowledgeable people here and most will help with questions you may have.

As for your Washington, I don't know this for fact, but there shouldn't be any issues running this on your 50 ohm antenna.
I'm sure someone who actually knows, and can explain it, will chime in.

I didn't think it would be a problem...a couple ohm difference on a 30 year old radio. I'm interested in hearing why, or why it doesn't make a difference.

 

[Brother DXer]

I didn't think it would be a problem...a couple ohm difference on a 30 year old radio. I'm interested in hearing why, or why it doesn't make a difference.

I agree.
I've been running my Uniden Washington on the A99 for some time now and have never given it a second thought.

 

[TM86]

Welcome aboard, Captain Kirk!

The whole 50 vs 52 ohms is nothing to worry about. That 52 is what the manufacturer designed for as the "perfect" impedance. But you notice they don't say what specific frequency? In reality anything close to 50 ohms is considered "good enough". And since impedance is a function of frequency, that number will change as you go up and down in the channels. Which is why when you check SWR you check on 1 and 40 to see which way to adjust the antenna.

Without going into a lot of antenna theory that I don't actually know, the closer you are to the "perfect" impedance the more efficiently power will be coupled into your antenna system. Also, the less power will be rejected by the antenna system into your radio. Which is why, with 12 watts max output on sideband (legally), CBer's obsess over SWR. Best match puts max power into the air, and less reflected power means the final output transistor runs cooler and will hopefully last longer.

To get more into the particulars of why 50 vs 52 ohms doesn't matter, a 75 ohm antenna would get you a 1.5:1 SWR reading. A 100 ohm antenna would get you a 2:1 SWR reading. So 50 ohms vs 52 ohms would get you somewhere around a 1.04:1 SWR reading, which anybody would consider a pretty darn good match.

TL;DR: It'll be fine.

 

[Capt. Kirk]

Welcome aboard, Captain Kirk!

The whole 50 vs 52 ohms is nothing to worry about. That 52 is what the manufacturer designed for as the "perfect" impedance. But you notice they don't say what specific frequency? In reality anything close to 50 ohms is considered "good enough". And since impedance is a function of frequency, that number will change as you go up and down in the channels. Which is why when you check SWR you check on 1 and 40 to see which way to adjust the antenna.

Without going into a lot of antenna theory that I don't actually know, the closer you are to the "perfect" impedance the more efficiently power will be coupled into your antenna system. Also, the less power will be rejected by the antenna system into your radio. Which is why, with 12 watts max output on sideband (legally), CBer's obsess over SWR. Best match puts max power into the air, and less reflected power means the final output transistor runs cooler and will hopefully last longer.

To get more into the particulars of why 50 vs 52 ohms doesn't matter, a 75 ohm antenna would get you a 1.5:1 SWR reading. A 100 ohm antenna would get you a 2:1 SWR reading. So 50 ohms vs 52 ohms would get you somewhere around a 1.04:1 SWR reading, which anybody would consider a pretty darn good match.

TL;DR: It'll be fine.

Thanks for the reply. It raises another question that I was gonna ask later because it's not about the Washington. I installed a small Cobra 19 in my Jeep recently and have it hooked to a 4' Firestick. I cut the excess coax and resoldered the tip. I checked grounding and continuity and everything seems OK. The SWR was way off. I clipped wire out of the tip a little at a time and got things at 2.0 on 1, 1.8 on 20 and 2.0 on 40. My understanding is that the goal is to balance SWR on 1 and 40. 2.0 seems high to me still but I don't know what to do about it. I don't know if me cutting the coax is causing this problem. I bought a K-30 with magnet base for a portable system I'm working on. I was gonna try this in the Jeep to see if it makes a difference. Thanks for your help.

 

[TM86]

Thanks for the reply. It raises another question that I was gonna ask later because it's not about the Washington. I installed a small Cobra 19 in my Jeep recently and have it hooked to a 4' Firestick. I cut the excess coax and resoldered the tip. I checked grounding and continuity and everything seems OK. The SWR was way off. I clipped wire out of the tip a little at a time and got things at 2.0 on 1, 1.8 on 20 and 2.0 on 40. My understanding is that the goal is to balance SWR on 1 and 40. 2.0 seems high to me still but I don't know what to do about it. I don't know if me cutting the coax is causing this problem. I bought a K-30 with magnet base for a portable system I'm working on. I was gonna try this in the Jeep to see if it makes a difference. Thanks for your help.

I use mag mounts, because I'm lazy. So most of what follows is stuff I've learned here over the last few years.

For a car, the antenna uses the body as the counterpoise, if the antenna is well grounded to the car body. Otherwise it uses the coax or some combination of car body and coax. Also, not all car bodies are the same when it comes to consistent ground. The body may not have a sufficient path back to the battery negative terminal for RF from the antenna to find it from the point your antenna is mounted. There's process that can be done to bond the various bits of a car together electrically, and it involves braided wire straps and possibly removing a bit of paint around bolt holes. I've been lucky in that I haven't had to do this.

When the car body as a ground for the antenna is insufficient, it will use the outside braid of the coax for it's counterpoise. When that happens the length of the coax may have an affect on SWR. There's a few mag mounts that seem to rely on this effect as well.

As for why your antenna won't get much below 2:1, I have no idea. Your best match is at channel 20, so you've done as well as you can for that particular combination of antenna and vehicle as it sits. So, yeah, try the mag mount and see if it improves the situation any.

For better advice, ask in the CB Antennas topic. There's a few contributors in there who really know their stuff.

 

[Capt. Kirk]

I use mag mounts, because I'm lazy. So most of what follows is stuff I've learned here over the last few years.

For a car, the antenna uses the body as the counterpoise, if the antenna is well grounded to the car body. Otherwise it uses the coax or some combination of car body and coax. Also, not all car bodies are the same when it comes to consistent ground. The body may not have a sufficient path back to the battery negative terminal for RF from the antenna to find it from the point your antenna is mounted. There's process that can be done to bond the various bits of a car together electrically, and it involves braided wire straps and possibly removing a bit of paint around bolt holes. I've been lucky in that I haven't had to do this.

When the car body as a ground for the antenna is insufficient, it will use the outside braid of the coax for it's counterpoise. When that happens the length of the coax may have an affect on SWR. There's a few mag mounts that seem to rely on this effect as well.

As for why your antenna won't get much below 2:1, I have no idea. Your best match is at channel 20, so you've done as well as you can for that particular combination of antenna and vehicle as it sits. So, yeah, try the mag mount and see if it improves the situation any.

For better advice, ask in the CB Antennas topic. There's a few contributors in there who really know their stuff.

Thanks for that info. I knew grounding was important and I checked continuity between the mount and the fender and it was fine. There could be an issue between the fender and the battery though...I will check that. I'm new here and haven't had a chance to look around. It's good to know that there's an antenna specific topics area. Thanks, Kirk

 

[Capt. Kirk]

Thanks for that info. I knew grounding was important and I checked continuity between the mount and the fender and it was fine. There could be an issue between the fender and the battery though...I will check that. I'm new here and haven't had a chance to look around. It's good to know that there's an antenna specific topics area. Thanks, Kirk

Well, well, well...what do we have here on the jeep. I've seen that grounding strap for years...goes down behind the engine. It just lifted right out of there. Don't know if it's the culprit but I do know it needs to be hooped up.

 

[Cable Guy]

Put that ground strap to the engine. Mine runs to a stud on the transmission|engine mounting flange. Anywhere it can touch the block is best. I'd put a ring connector on the braid and attach it to that stud on the exhaust manifold or extend it with braid and attach directly to the block. Wire brush the area to clear rust, oil and/or paint before attaching.

 

[Cable Guy]

Also, if using copper or clad ring, to aluminum, use penetrox or similar compound to keep the dissimilar metals from reacting.

 

[Capt. Kirk]

Also, if using copper or clad ring, to aluminum, use penetrox or similar compound to keep the dissimilar metals from reacting.

Great idea! I figured it went down to the bellhousing and after changing out a few CPS's in my life I knew going back down there would be a nightmare. I think some of those head bolts have additional threads on top. That would be a perfect spot. I'll run out in a bit and get a parts list together. I have noticed some intermittent static on the CB when I'm driving on bumps and around corners not sure if poor grounding can cause that but it's worth a shot.

 

[Cable Guy]

Could be the braid flapping about in there. Sounds like you have it figured out now. Let us know how you get along.

 

[Capt. Kirk]

Could be the braid flapping about in there. Sounds like you have it figured out now. Let us know how you get along.

I'm not going to touch the radio or antenna at all. I'll hook that ground back up and see if that does anything with the 2.0 SWR and post the results here.