base radio pre amp install

[johnny9]

i installed 1 of 2 small pre amps i have..question is to make sure its ok there with a amp in the future.the way i installed everything is per this forum"thanks"and just added the pre amp.

got pre amp to back of the radio.
ant side pre amp to xmtr side of amp
ant side of amp to power meter
meter to antenna

everything works great like this just wanted to make sure it sounds correct,and mainly that when i ever use the amp it cant hurt the pre amp..these lil dinasour pre amps really make a difference..thanks,j9

 

[M0GVZ]

Unless your S meter reads S0 with the preamps turned off you don't want to be using them at all.

Not only do they increase the wanted signal but they also increase the noise and nearby unwanted signals and all you're doing is reducing the signal to noise ratio making signals, especially weak ones, harder to hear. You would do far better to lower the RF gain and turn the volume up if you're trying to hear weak signals. Turning the RF gain down whilst it does weaken the wanted signal, the noise drops even more, improving the signal to noise ratio and making them more readable.

Pre-amps have virtually no use on HF frequencies because of the noise on the bands.

If you insist on using a pre-amp you want one right at the antenna, not at the radio end where it is also amplifying the noise the coax is picking up as well.

If you're using a single element vertical, changing to a beam will give you far better results than a pre-amp and it'll be beneficial on both transmit and receive.

 

[johnny9]

my meter is a 70,s rs micranta 10/100/1000 watt/swr meter..i do insist on using the pre amp as it does a great job and i can hear better since my antenna is kinda low for now..
so your saying i need to install the pre amp after the meter closest to the antenna in your reply?
i assume when i someday use a amp it wont hurt the pre amp then,that was my worry of not wanting to hurt the pre amp..its old and works great with the "on the air" lighted face..i like the old cool stuff myself lol.
my antenna is a 70,s astro plane in perfect cond,but its real low"15-18ft at the moment but will be soon on a crank up small tower,maybe tomorrow if i light a fire under my butt.
then i may not want the pre amp..it does cause more noise but when i cant hear anything at night,and turn on the preamp i hear a lot,so it def helps imo..thanks j9
btw this is just for 11 meter cb use

 

[Captain Kilowatt]

M0GVZ is correct in stating that the best place for any preamp is right at the antenna before the feedline to the shack. That being said, since this is just for CB it will likely work just as good (bad?) in the shack. In any case if it will not handle much power you do NOT want it after any amplifier. I have used a preamp in the shack before and it worked well however this was for VHF at 2m and the feedline was heliax cable so the loss from the antenna to preamp was next to nothing, less than 1 dB, and feedline pickup was nil. It was a low noise GaAsFET preamp whereas most CB type preamps are of much less quality and often actually degrade the minimum noise floor of the radio itself and simply either add noise or amplify the noise as much as the desired signal. If it an above average quality CB preamp it may work well when the band is quite. The real test is to try it out on a really weak signal on a quiet band and actually listen for a change in signal and disregard any change in meter reading. If the meter jumps a few S-units but the signal does not sound any better the preamp is not really doing what it should.

 

[johnny9]

got it,thanks..imo it makes a huge difference.i put it closest to the antenna and have a sligh higher swr reading with it there,but not enough to matter..i just hope when i test the new amp it dont harm it..
its my fav of the 2 i got..there both communications power inc.range plus units..look old but work great,merry christmas to you all at wwdx,j9

 

[johnny9]

cool,not sure why but noticed this morning that since i moved the preamp to he antenna end my meter says im getin a extra watt out..checked with another meter to confirm
not sure why,but i"ll take it

 

[binrat]

cool,not sure why but noticed this morning that since i moved the preamp to he antenna end my meter says im getin a extra watt out..checked with another meter to confirm
not sure why,but i"ll take it

That extra watt, no one will see the difference.
Sent from my GT-S5690M using Tapatalk 2

 

[johnny9]

but it makes me feel good looking at the meter lol..i cant talk anyhow,just listen to the worldwide trash talk :laugh: getting everything in order and getting close tho.

 

[Shockwave]

cool,not sure why but noticed this morning that since i moved the preamp to he antenna end my meter says im getin a extra watt out..checked with another meter to confirm
not sure why,but i"ll take it

There is no extra watt. The meter is just being tricked by the slightly higher SWR with the pre-amp inline. Any change in SWR will also cause a change on the power meter. Watt meters can only be accurate when they are operated into a 50 ohm load or flat SWR.

 

[johnny9]

thanks,i learned something on christmas day already i have a perfect flat swr till running thru the amp,then it goes to 1.3 or so..
happy holidays

 

[M0GVZ]

thanks,i learned something on christmas day already i have a perfect flat swr till running thru the amp,then it goes to 1.3 or so..
happy holidays

If you only see the SWR rise when you put the amp in line it may need the input match on the amp (one you plug patch lead from rig into) tweaking a little although I'd not worry.

 

[johnny9]

thank you