SWR question (Midland 75-822 CB)

[Grant]

Hey, all, I was putting the new Midland in my car, and I was tuning the mag-mount antenna (also Midland, center of the roof) with a little SWR I have. The SWR is a bit below 1.5 on both 40 and 1.

On the power meter on the radio, though, it shows full power from Channels 1 to 20, and much above 26 to 40 it shows less than full output. This is after I disconnect the meter, with the meter it shows full on all channels.

I did originally have full output according to the radio on all channels, but the SWR meter also shows that antenna setting in the red, which I know isn’t good.

Is there an adjustment I’m missing, or is this actually right? Maybe it's the extra foot of coax the meter uses? I have no idea how to compensate well enough for that.

[TacAir]

One of those "it depends."

May I suggest that you adjust for best (LOWEST) SWR at Channel 20 (out of 40)

Back check for SWR at Ch 1 and Ch 40.

Some of the issues involved might be with the SWR meter you are using.
In my experience, the CB SWR meters are of questionable quality for the most part, but will work. If you can borrow another meter to double check - might be worth the effort.

If the cable for the meter is making a difference, you need to confirm that you have a good ground for both the radio and antenna. Check the connector to ensure it has a good fit, isn't loose, and give it a light tug to ensure the connector has a good mecanical connection as well.

I'm not familiar with your radio, but some radios power meters are more of a guess than not. IF it is a quality meter setup, some radios will slightly reduce power output if the SRW exceeds some value set at the factory (foldback) - so, maybe borrowing a meter to double check might be worth the effort.

Finally, IF you can bond the antenna (run a ground wire from a roof rack to the base of the antenna) to the vehicle ground, likely you will see an improvement.

Hope this helps...

[williaty]

May I suggest that you adjust for best (LOWEST) SWR at Channel 20 (out of 40)

Back check for SWR at Ch 1 and Ch 40.

If he has roughly equal and semi-low numbers on 1 and 40, he's almost certainly centered on 20 as the SWR vs Hz curve is parabolic.

Some of the issues involved might be with the SWR meter you are using.
In my experience, the CB SWR meters are of questionable quality for the moist part, but will work.

If your meter comes with a moist part, it's DEFINITELY of questionable quality

Seriously, though, I agree. Either the radio's wonky or the meter is wonky. Try a different meter, see what it has to say.

[KJ4VOV]

Try using a shorter or longer piece of coax to connect the meter and see if that changes anything. I have a feeling you're getting a little resonance there.

[gary in ohio]

1.5 SWR across the band is fine...

[terminaltransco]

1.5 SWR across the band is fine...

i'd agree, folks always told me that lowest is of course best, but anything under two and your fine. that is weird though that with the meter plugged in he noticed a power difference in the upper channels? hugh, that one makes me scratch my head.....

[crypto]

Every one of the dual-use SWR / power meters Ive ever used have been shitty at power readings, to be honest.

Id be interested in hearing how this pans out though, because this Midland unit is the same one I have for road trips, and I've recommended it often.

[Grant]

I meant the power meter on the Midland when on TX shows less than full on 35-40 (at the moment), I tried to re-tune the antenna a bit. It's now full on every other channel. Not sure why this is. With the rubber duckie it's full on every channel, so it's obviously the external antenna. I CAN get it to full on every channel, but then the SWR is close to 2.5 and unbalanced.

I guess I'm better off with a balanced SWR than a full bar on the radio itself? It seems to work fine but I don't want to damage my CB with a bad tune.

[williaty]

/me facepalms


It's a Midland. What's your RF Gain set at? The Midland power meter actually correctly displays the reduced output power when you turn down the RF gain (since they do RF gain kind of weird in that it's bi-di). If you bumped it, that might be your issue.

[Grant]

No RF gain in this model that I know of, it's a simple portable that I'm using with the mobile adapter after seeing good reviews here (it's not a high-end CB, it's for me, a guy who will use it for roads and weather more than anything else).

[williaty]

Weird. Midland's cheapest model (1001Z) has RF Gain.

[aa1pr]

Most finals in all radios will produce more power in a certain frequency range.

However I doubt it in a cb though, I would think it lies in the swr/power meter as being inaccurate

test the power output across the frequency range into a dummy load & see what happens

I think this will help you discover what is really happening

[Grant]

It does appear that the meter is inaccurate towards the lower channels. Not sure why. But the radio's working great now and I just went 700 miles and was able to hear events ten-plus miles in front of me, no problem. Haven't actually TALKED to many people, but that will come later.

Thanks all, for the help and the radio recommendation! The Midland handheld/portable wasn't even on my list, but for my use (mostly in the car, occasionally as a field radio when in the outdoor labs and never both at once) it will do great and saves me some money while I'm at it as one radio becomes two for me.

[buck85]

It answered some of my questions too