Can someone explain this to me

[psycho]

I normally run a Cobra 148 GTL with a Worldwide MF-80 and a Worldwide MF-400 4 pill. I run a dead key with the amp at 200 watts swinging to 450 watts on a Bird 43.
A friend bought a new Connex 3300 HP and had a variable key put on it and a real nice peak and tune. My 148 keys 1 watt and swings 9 watts on a Bird 43 but the Connex keys 1 watt and swings 14 on the same meter.
So far so good.
When I run the Connex variable set so the amp keys 200 watts it'll only swing to 380 watts on the same meter.
Both radios swing to their individual max whether they are keying 1/2 a watt or 7 watts.
The same thing happened with a DeltaForce, 2510, and Galaxy 88....more output barefoot and less output with the amps on.
Is there something about export radios that we are missing.
All these tests were done in the same vehicle with the same setup.

 

[AA1QD]

I would look at what the other radios do for rms power at the setting to make the amp key 200. I would expect the 148 is doing more forward rms power.

 

[ss8541]

the amp is not displaying the same impedance as the antenna or dummy load you tested the radios into. in other words, the connex is most likely delivering less power to the amp than the 148 because of the impedances that the amp is 'showing' to the radios. and of course if the connex is actually delivering less power to the amp, the amp will put out less power as well.

to see what power the radios are actually delivering to the amps you would need two 1/2w sections of coax with the watt meter in the middle and the other ends going to the radio and amp. this lets the radio and wattmeter see a mirror image of the amps input (but they will be 180* out of phase with each other).

on a side note, you most likely can play with jumper lengths until you find a 'sweet' length that displays an impedance to the connex that it likes better and allows it to deliver its full power to the amplifier.

 

[Happy_Hamer]

on a side note, you most likely can play with jumper lengths until you find a 'sweet' length that displays an impedance to the connex that it likes better and allows it to deliver its full power to the amplifier.

Richard would something like this work with these amps?

This basically "fools" the radio correct? But is it worth the trouble to install into an amp? I just think its a cool project.

www.ldgelectronics.com/products.php?cID=1&pID=2&v=1

The LDG AT-100AMP now offers homebrewers the opportunity to include a fully automatic tuned input stage in their amplifier. Similar in performance to the popular LDG AT-100Pro, the AT-100AMP is customized for use in the input stage of an amplifier. Designed to be built into the amplifier, it offers fully automatic operation, and requires only three connections: 12 vdc, RF in and RF out. The AT-100AMP automatically tunes the input of your amp in seconds so the exciter is always optimally matched to the amp. As you operate, the AT-100AMP's 4,000 memories store tuning parameters for your favorite bands and frequencies for nearly instant recall when you transmit on or near the same frequency again. The AT-100AMP can handle up to 125 watts RF input, but requires only 0.1 watts to tune

 

[ss8541]

that is exactly what this product does. this would eliminate the problem 'psycho' is seeing with his equipment.

you can also take a basic antenna matcher (matchbox) and put it inline between the radio and amp and have the same results. it is transforming the input impedance of the amp to an impedance the radio is happy with.

 

[freecell]

"it is transforming the input impedance of the amp to an impedance the radio is happy with."

and what the radio transmitter is happy with is being able to deliver all available power to the load, whatever it is. when the input impedance seen at the transmitter most closely resembles its own output impedance then the radio transmitter is happy.

 

[BOOTY MONSTER]

is this something that happens often ? will the AT-100AMP or the antenna matcher allow the amp to have the same high power again as the cobra was getting vs the exports ?
since i only have one radio and one amp , can or how would i check this on my system and is it something that can cause damage , or just cause the loss of a few watts ?

 

[psycho]

I would look at what the other radios do for rms power at the setting to make the amp key 200. I would expect the 148 is doing more forward rms power.

The Connex is swinging forward almost twice the RMS of the 148. Nevertheless the 3300 HP is 1 loud radio with or without the echo.
Even with the possible impedance issues and the reduced output of the amp the audio is highly impressive.