SWR fluctuates from day to day

[Rred]

(SLAP!) D'oh! Yes, Type N is what I meant.
Memo, no more decaf.

Snow-
You'd want to either get a new premade cable, or lop off the far end and change it to TypeN connector. Of course the connector on the radio stays the same, unless you REALLY want to "do it right" and change all the connectors including the one on the radio chassis. (Which shouldn't need waterproofing anyway.) A new cable (again, from a quality supplier) that they put the fittings on, probably is worth the cost.

Yes, using a UFH-to-N adapter at the base of the antenna may provide a slight loss and a place where something else can go wrong, but overall it would allow keeping the antenna, and in that type of situation a connector/adapter usually is pretty reliable. Assuming you buy it from someone like Amphenol, not "two guys in Shenzhen who like much eBay!".

It is easy enough to secure that properly, and overcoat the entire adapter with "liquid lectric" or a similar vinyl or rubber coating. It won't move, it won't leak, and the part that MIGHT have to be removed in the future is the cable, with the waterproof TypeN fitting on it, so overall it should be more reliable.

 

[JayMojave]

Hello Rred: This is a new guy he just needs to get going, he can upgrade and get new stuff later.

So what is the insertion loss S21 difference between the PL259/SO239 as compared to the N type male female connectors. So if the insertion loss is known then we can dial that into how much it will effect the Transmit / Receive.

The connectors are placed near the radio and antenna, these are figured / tuned into the radio and antenna matching circuits. I have replaced the PL259/SO259 connectors and didn't see any difference. Did I miss something and not see a major difference?

Jay in the Mojave Desert

 

[Rred]

I don't it Jay. You replaced the UHF connectors with...what? And why? And did you have them on RG8 or other thick cable, or thinner cable with adapters? All of thatcan make differences in the inmpedance matching, These aren't "figured into" the matching circuits, those circuits simply accommodate mismatches and impedance bumps as best they can. Matching them, sure, but always with losses.

Remember that I didn't suggest the TypeN connectors to eliminate losses, I suggested them mainly because they are inherently WATERPROOF and he's got a water intrusion issue.

As to exact losses at CB frequencies (which are near the 30MHz design limit for UHF cables) and exact impedance differences, you can google that yourself. (No offense meant.) Try starting at Amphenol. I had called them years ago to ask a similar question about using FME connectors or lower loss thicker coax in mobile installations, and got a fast education into impedance bumps and why some standards are best left alone.

Audi R8, Karman Ghia, all look alike from the outside. Then a Nissan GTR whips by on the curves and you say "WTF?! What was THAT?"

UHF connectors will do the job for CB. But, if they are not doing the job (i.e. water intrusion) then there are alternatives which will eliminate the problem. Unless of course, like everything else, they're cheap stuff poorly implemented. Proper crimping/soldering/sealing seem to be rocket science for a lot of folks, including ones who are in the business and then selling their goods.

SWR can be deceptive. It really only tells you how much power was bounced back AND reached the transmitter. If the antenna "ate" a lot of power in losses, or if the cable (including fittings) "ate" a lot of the returned signal, your SWR can be a perfect 1:1, and the antenna still will put out like a fencepost.

Some folks say "Oh, a 3db power difference is nothing...." while others pursue each 1/2 db at a time. Each to their own.(G)

 

[JayMojave]

Hello Rred: Wow I did make a incomplete and vague statement, I stand corrected. Yes it wasn't you.

I have found that even the N type connectors with there O-Ring need moisture protection as do the PL259 connectors.

The PL259/SO239 connectors on a antenna were replaced with N Type Female and Male, and I did not see any real difference between the two types of connectors. So replacing the PL259 with a N type connector at these lower frequencies is not practical.

The impedance bump of the PL259 connector can be measured and compared to the N type connector sweeping the frequency say from 1 to 1000 Mc and comparing the insertion loss's. I am sure at the CB Frequencies it isn't a hole lot. And yes the impedance matching circuits can and will help tune the impedance bump, how could it not.

I will watch myself more closer in my postings, not being vague and leaving important stuff out. Thanks.

Jay in the Great Mojave Desert

 

[bharvey2]

Another stupid question to go with this. I am running my radio off a 12 volt battery in my house; however, I charge it with a trickle charge charger on a constant 2 amps charge. If I can do it through the 12 volt battery, why can I not just hook the trickle charger directly to the radio's power supply? I have a 5 amp inline fuse between the battery and the radio.

While the trickle charger provides the desired 12VDC, it is very likely that the rectification (converting AC to DC) and filtration (smoothing out residual AC ripples to make a pure DC voltage) may not be adequate to power your radio.

When I was a teenager, I powered my first CB the same way: battery and charger. The battery acts as a filter for the charger. Without the battery, the charger would still power the radio but a very pronounced hum was present in the audio on both transmit and receive. There is no reason however that you couldn't find an appropriate power supply to run your radio.

 

[Rred]

J-
Odds are that in any type connector, there are quality differences that won't be visible, or won't be easily visible. That could be one reason you had leaks past the O-rings. Or assembly issues, soldered or crimped not quite right. Even with sealing, some folks swear by coax-seal, others call it junk and want electrical tape plus silicon tape, although the telcos insist on butyl tape. So, no single absolute best way.
Impedance matching accomplishes a purpose, it matches impedance so among other things reflected energy won't blow out a radio, i.e. SWR matching. But there's always a price to be paid for it, some power is consumed by the device so some output is lost. Better, when possible, to make a system that doesn't need one. But of course that's not always possible either.
The more I find out about antenna theory the more it reminds me of a sausage factory: Everyone wants the final product for breakfast, no one really wants to spend time getting the factory tour. For good reason.(G)

Snow-
You may find another reason not to use the trickle charger directly. Most "12" volt radios are designed to run on 13.8V +-10%, sometimes 15%. Not really 12 volts, and at 12 volts they often start to get noisy or drift off frequency. But a "12" volt charger may actually put out 14.4 volts or vary higher or lower,depending on what charging algorithm it is using. It might be varying the output voltage based on the battery it sees--and it won't see one if you hook it up directly. So there are more numbers you have to run, to make sure if it would work. Even IF the power output was clean enough, and you can't easily tell that. Twelve volt power supplies are cheap enough, better to take your chances on something designed as one.
All this stuff (cables, batteries) works "well enough" most of the time, but if you really want it to work 100% and all the time, there's a lot more than meets the eye.

 

[jonwienke]

Using a battery charger as a power supply gets even messier when the charger has conditioning cycles programmend in. Lead-acid chargers sometimes vary the charge voltage significantly when doing a desulfation cycle, and several types of chargers use pulsed charging current to prevent/reduce electrolysis of the water in the battery electrolyte. None of these features are helpful or useful when using the charger to run the radio directly.

 

[SnowWalker]

I think I am beginning to suffer from brain overload!

 

[wb6uqa]

Bad connection . Check all with a Ohm meter. Tape all out door antenna connectors. Don't blow your finals.

 

[cmdrwill]

Bad connection . Check all with a Ohm meter. Tape all out door antenna connectors. Don't blow your finals.

Adding, improper connector installation, poor quality 'PL259 type' connectors with insulators that suck moisture.

 

[JayMojave]

Hello All: I'll ask this again:

Hello Cmdrwill: Got a part number for that "good one" crimped shield, soldered PL259 connector and crimping tools needed. From RF Industries, and a distributor, and a price?

PL259 connectors are used all over the place, even on new ham radios and such. Whats the real world?

Jay in the Great Mojave Desert

 

[Rred]

UHF RF Coax Connectors Product

That's the RFIndustries.com secrete catalog page for UHF connectors. Some crimp, some solder, at least one even claiming to be waterproof, many specific to single cable sizes.

 

[mmckenna]

Hello All: I'll ask this again:

Hello Cmdrwill: Got a part number for that "good one" crimped shield, soldered PL259 connector and crimping tools needed. From RF Industries, and a distributor, and a price?

PL259 connectors are used all over the place, even on new ham radios and such. Whats the real world?

Jay in the Great Mojave Desert

You can pick up the "RF Industries" brand connectors from Tessco. I think I've got a few in my garage. Although none of my gear uses PL259/UHF connectors any more, I keep a few on hand for making adapters or doing the rare install.

As for the "real world" you will rarely see UHF connectors on anything made in the last 20 years. Some lower end commercial radios still use them, especially on VHF and UHF radios. If you start getting into 700, 800, 900MHz, or higher end gear, you'll see different connectors. N connectors are getting more popular and the ever present Motorola "mini-UHF" connectors.
On the radio site end, everything will be N connectors for the smaller stuff. The 7-16 DIN connectors are getting very common and are almost the only thing you'll see at a cellular site.

 

[JayMojave]

Hello All: Ok good deal on the info here, greatly appreciated.

I was hoping cmdrwill would tell us his opinion of the "good one" and the "real world" since he said these things without giving assembly details, or part numbers! Hoping for some good insight.

I am familiar with these said connectors, use to use LC connectors on 7/8 Heliax Coax for long runs on mountain tops for repeaters and such, then switching to 7/16 Din connectors, even for RG213 / RG393 type coaxes. Have used the Crimp shield, soldered center pin, N type connectors with good results. I know there are crimp center pin type designs, but I prefer the solder center pin types.

And most all connectors need water proofing, even the ones with the O-rings and such, black tape works wonders. Heat shrink boots need added RTV back up sealer.

Jay in the Great Mojave Desert

 

[cmdrwill]

RF Industries number RFU-505-ST for RG 58 size cables.

What I was attempting to illustrate is the insulator between the center pin and the housing. The PTFE and Delrin are the better insulation materials. The black and brown will absorb moisture and do not have good insulation for RF above 30 mHz.

For RG8 and RG213 cables:
Show Product

" The 'good ones' " have a full center pin as shown in the second photo.

 

[JayMojave]

Yo cmdrwill: Yeah thats the stuff.

The connector "Drawing" gives the crimping tool info and crimp type die dimension needed. I would think that the crimp tool and die are the same for the N type connector. Buts that's another story...

Jay in the Great Mojave Desert Miss Dinah's fillin station now has heavy jackets, and cold weather gear and stuff as the weather has gone from the Mojave Desert Hot, to Sargent Preston of the Yukon Territory Cold and windy. Gas is at 2.85 a gallon and holding.