CB Signal meter question

[niceguy71]

getting my mobile going... grounding the pick-up truck this weekend... and I have Best Buy wiring a relay on the 16th so when I turn the key on it will let power go directly from battery to CB... for now it's wired to the cigarette lighter... anyway....
I've got the SWR decent for now.............. my neighbor saw me putting a CB antenna on my truck so he put his on his car... I was going out to supper 20 miles away so I said I'll talk to you on the way and see how far we get.... this was at 3:30PM and I think the CB conditions were not good.... my signal meter on the CB was at 7 on all channels... .. we talked for 3.5 miles .... I noticed every time I keyed my mic the needle on the meter would only go to 5 to 7???? it normally goes into the red almost full scale when I talk on it???? so after I had supper I'm heading home and try to get my neighbor and noticed the conditions were now good... and my Signal meter when I talked was now going just about full scale again???? does atmospheric conditions change what my transmitting meter will show???? I never knew this if that's what happened???? or was this just a coincidence? ???
SWR picture just for a before... and I'll see if RF bonding the 4 corners of the bed to the frame... four corners of the cab to the frame and bonding the bed to the cab.... also bonding the hood and fenders..... and adding a few better grounds....I'm not moving the antenna and I'll see what the SWR is after this weekend.

 

[prcguy]

Power meters in the radio are simply a diode detector before the coax connector and the resulting rectified voltage is sent to a meter and adjusted at the factory when the radio is feeding a 50 ohm resistive load. Once calibrated the power meters can be very accurate on dead carrier power. However, connect the radio to an antenna with impedance all over the place plus the effects of capacitive and reactive reactance and the simple diode detector will read all over the place even though the power out of the radio is the same.

Here is an example of what can happen. 4 watts of carrier into a 50 ohm resistive load puts 14.14 volts at .28 Amps of current across the resistive load. Change that resistive load to 60 ohms and now the voltage will be 15.49 volts at about .26 Amps of current. Since the radio power meter is detecting RF voltage near the CB antenna connector raising the antenna or load impedance will make the meter read higher even though the RF power is the same.

Your antenna will have different characteristics between ch 1 and ch 40 so I would expect the power meter to read different across the CB band. Its just a fact of life so don't get too caught up in it.

 

[niceguy71]

Power meters in the radio are simply a diode detector before the coax connector and the resulting rectified voltage is sent to a meter and adjusted at the factory when the radio is feeding a 50 ohm resistive load. Once calibrated the power meters can be very accurate on dead carrier power. However, connect the radio to an antenna with impedance all over the place plus the effects of capacitive and reactive reactance and the simple diode detector will read all over the place even though the power out of the radio is the same.

Here is an example of what can happen. 4 watts of carrier into a 50 ohm resistive load puts 14.14 volts at .28 Amps of current across the resistive load. Change that resistive load to 60 ohms and now the voltage will be 15.49 volts at about .26 Amps of current. Since the radio power meter is detecting RF voltage near the CB antenna connector raising the antenna or load impedance will make the meter read higher even though the RF power is the same.

Your antenna will have different characteristics between ch 1 and ch 40 so I would expect the power meter to read different across the CB band. Its just a fact of life so don't get too caught up in it.

Thank you PRCguy... but I was using the same channel both times nothing changed... only difference was a couple hours of time and the atmospheric conditions.... I just thought it was strange the needle would go halfway in the afternoon and all the way in the evening??? 3:30 versus 6:30Pm

 

[mmckenna]

Were you driving at the time?

The antenna flexing back can change things. Also, make sure everything is tight.

 

[niceguy71]

Were you driving at the time?

The antenna flexing back can change things. Also, make sure everything is tight.

Hmmmmm .,,....I was driving when I saw the needle halfway, on the highway... then when I left I checked it in the restaurant parking lot .... Everything is tight.,...... Could it be that easy???... Thank you .... I never saw my cb do that in the 90s with my K40 mag mount ... But the antenna was to stiff for my garage door so I got a highly rated Tram 3500 with a véry flexible antenna ... I never thought about that

4C

 

[mmckenna]

Well, not sure that is it.
But check it without the truck moving and see how it does.
Then check it while driving.
Just a guess on my part.

 

[2RT819]

I would suggest that you wire your radio straight to the battery. Cigarette lighter sockets are poorly grounded and not the proper gauge wire. I would also keep the fuse at the battery connectors.

 

[niceguy71]

I would suggest that you wire your radio straight to the battery. Cigarette lighter sockets are poorly grounded and not the proper gauge wire. I would also keep the fuse at the battery connectors.

having that done in two weeks as I said in my post..... Best Buy is a great electronics store and has the best audio install department around... I kept trying to figure out how to mount a relay so if I shut the truck off the power to the radio will go off too and then get through all the wires in that firewall... I have a Best Buy Total Tech package so they do installs for me for free.... so in two weeks I'll see if that makes a difference 2RT819

 

[mmckenna]

Even BestBuy should be able to handle that, but check their work carefully. Stereo shops have an extremely bad reputation in the two way industry for doing truly awful installations. I've had to fix a bunch, and I know many others on here have. An actual two way radio shop will do a much better job.

As for the relay, that's a good option.
Other choice is to get a ChargeGuard or Lind Timer. It's essentially a relay with a timer. You can set the timer to leave the radio powered up for a certain amount of time after the ignition is shut off. Most also have a low voltage disconnect.

Protect Your Fleet from Dead Batteries This Winter With ChargeGuard | Havis Inc

Protect Your Fleet from Dead Batteries This Winter With ChargeGuard | For customer support, call 1.800.524.9900.

www.havis.com

https://lindelectronics.com/product-category/shutdown-timers/?inv_value=11-16&stand_rug=standard

 

[slowmover]

“ . . my neighbor saw me putting a CB antenna on my truck so he put his on his car... I was going out to supper 20 miles away so I said I'll talk to you on the way and see how far we get.... this was at 3:30PM and I think the CB conditions were not good.... my signal meter on the CB was at 7 on all channels... .. we talked for 3.5 miles ...”


With AT5555-N2 & (2) 8’
SIRIO 5000 (13’ 11” TTL height) on my end:

Post in thread '2023 Best Mobile CB'
2023 Best Mobile CB

We found an empty channel on USB for this early test in more to come, mobile-to-mobile.

Big trucks are notoriously more difficult. You “should” be able to meet or beat this given decent conditions and favorable topography.

Sideband performance is just as important in regional (local) comms as shorter-range AM (or, FM). To other mobile units, but especially back to one’s home station as reassurance in family travel safety.

FWIW, 1500 to 1800 “can” be worst time of all for CB comms even in the absence of Skip. It’s also a very bad slot for serious road accidents to occur.

The clock time CB can be most necessary for early warning in highway travel sees many having turned off the radio, defeated by “noise” still amenable to being modified for clarity. (By 2023 standards, not 1989).

Your follow-up thread:

truck install finally done

I took the day off to figure out my base station antenna or buy a new Antron 99 with ground plane kit... it's rained all night and all day!!!! but this weekend I did finally finish my truck install after a few months...... I have been wanting my truck undercoated for years but I wanted to do the...

forums.radioreference.com

.

 

[slowmover]

“... and I'll see if RF bonding the 4 corners of the bed to the frame... four corners of the cab to the frame and bonding the bed to the cab.... also bonding the hood and fenders..... and adding a few better grounds....I'm not moving the antenna and I'll see what the SWR is after this weekend.”


Dont forget vehicle exhaust system. The majority of bonding help posts I’ve seen mention this. (Horizontal surface priority).

Here’s a kit example:

DX Engineering DXE-EGK-300 DX Engineering Exhaust Grounding Kits | DX Engineering

Free Shipping - DX Engineering Exhaust Grounding Kits with qualifying orders of $99. Shop Mobile Exhaust Grounding Kits at DX Engineering.

www.dxengineering.com

.

 

[niceguy71]

“... and I'll see if RF bonding the 4 corners of the bed to the frame... four corners of the cab to the frame and bonding the bed to the cab.... also bonding the hood and fenders..... and adding a few better grounds....I'm not moving the antenna and I'll see what the SWR is after this weekend.”


Dont forget vehicle exhaust system. The majority of bonding help posts I’ve seen mention this. (Horizontal surface priority).

Here’s a kit example:

DX Engineering DXE-EGK-300 DX Engineering Exhaust Grounding Kits | DX Engineering

Free Shipping - DX Engineering Exhaust Grounding Kits with qualifying orders of $99. Shop Mobile Exhaust Grounding Kits at DX Engineering.

www.dxengineering.com

.

my friends helping with the bonding asked if we should do the exhaust???.... and I had plenty of bonding straps... but after we got it done the SWR came down, no engine noise what so ever ( it was quiet before and the same after wiring directly to the battery... it was just never very noisy)....so I thought it was perfect and didn't think the exhaust would help much more. ... I want to test it to my base station when I get it up... but for now mobile to mobile seems about 5 miles on 12watts AM... not too happy with that... but it all depends on the radio I am talking too.... for all I know, I'm talking to the town garbage truck using a K-mart special....( Sorry K-Mart) but I think I am getting out well as every time I go out I try to get someone on 19 and so far almost always get someone... but they are at most 5 miles away..... I have yet to get anyone on Sideband 36 37 38 39 LSB,,, I try every night but my 27 Watts has not got it done yet... but I'm happy with my Pick-up install... I think it's the best it's going to be Slowmover