WATT's the problem

[onefastneonrt]

Well it did exactly what Cheech said, as I expected. With the radio untouched and the amp on I was pinched up. On low I was pinched and putting out 83 watts with absolutely no swing. On high I was pinched even worst and putting out 122 watts with no swing. I turned the amp off and ran bare radio with no problems. I figured that this amp was a limited production made behind closed doors at someone’s shop for a little extra cash (J&S CB Radios in Cali.). With that said I believe that it was a simple design with no extra care given to the drive circuit (no "padding”). Remember this is not a high end amp like a TS or Palomar. After reading the Cobra service manual again I am leading to believe that LT1 is used to adjust power. The VCO goes to a buffer amp which feeds a tuning circuit (LT1) that supplies the pre driver amp, RF driver amp, and the final. By changing the buffer amp tuning circuit you will change the radios overall output. Modulation is fed in at the RF driver and final circuits, after the buffer amp tuning circuit (LT1).

"the only method for re-shaping the peak-to-carrier output in the Cobra 19DX is to construct an RC shaping circuit and substitute it for the negative peak clipping rectifier in the transformer output that feeds the collectors of the driver and final stages simultaneously."

The buffer amp tuning circuit is basically doing the same thing but off the VCO.
I know for sure the amp likes low power drive and I think I'll hook up the meter and tune the LT1.

 

[9C1Driver]

That radio only swings 8 watts, you won't get much swing from ANY amplifier with 8 watts peak. I don't understand your test, if it worked on Low with 4 watts from a different radio then 3.5 on Low should work with the Cobra19.

You will have to have a tech add a resistor in that radio to dampen down the dead key alittle more I guess. Bottom line is thats not much of a radio really to start with. You would have been much better with a used Cobra 25/ Uniden 66,68 and so on.

 

[74IN]

8W isn't bad. Not on a Bird.

 

[freecell]

you use LT1 to lower the carrier the modulated power will drop even further below 8WAVG. or about 21WPEP. the 100HL is definitely not AB.

 

[onefastneonrt]

That radio only swings 8 watts, you won't get much swing from ANY amplifier with 8 watts peak. I don't understand your test, if it worked on Low with 4 watts from a different radio then 3.5 on Low should work with the Cobra19.

You will have to have a tech add a resistor in that radio to dampen down the dead key alittle more I guess. Bottom line is thats not much of a radio really to start with. You would have been much better with a used Cobra 25/ Uniden 66,68 and so on.

-The radio dead keys about 4 watts and swings to 8 with modulation bone stock, which is too much to drive the amp with. Your right I will not get any swing and as I am right now very pinched up on the modulation. I am trying to bring DOWN the overall wattage of the radio. The other radio that I had used with the amp was a Uniden PC76XL that originally put out 4 watts and I had experienced the same problems; pinched up, high peak wattage, and no swing. I had then turned down the wattage on the Uniden to 1.5 watts and the amp cleaned up nicely. This is what I am trying to accomplish out of the Cobra.

- The reason I am using the Cobra 19DX IV and not any others is because it's the only radio that will fit neatly into my car. The Cobra 25, 29, 148, 2000/Uniden 66, 68, 76, 78 are all just bigger than they need to be. I do not need all the bells and whistles that all the other radios offer. Memory, delta tune, echo, SSB, RB, mic gain, built in SWR, weather is not necessary plus I have all of that in or on my base.

- Not at all 74IN, especially out of a bone stock radio right out of the box.

Maybe I'll just go with the Uniden 510 and last resort a Magnum (Landmatic) 257, 357.

 

[onefastneonrt]

Well F-it I give up, both radio and amp are a P.O.S.
Both are for sale: Cobra 19DX IV (brand new), 100HL Amp (120w) $300 LOL

How's that for a solution.

 

[Switch Kit]

The HL 100 is anywhere between 20 and 15 years old , the first run models were called Marko's These were basic copies of the Pride amps and these were class C all the way. (unless Joe cleaned one up for you) They first came with the MRF 453s then the 455s and then 454's were also used.

Were they the best amps on the block ? No ! did they work and perform well ? Yes ! are they still around over 20 years later ? Yes ! Joe also used the Powerpump name on his amps as well (base and mobile units) This HL 100 likes about a 1 watt DK and it should work and perform well on hi or low (hi power or low power)

Freecells numbers are about right 30 to 40 to about 120 to 140 (depending on the radio used and how it was tuned) on Hi , Low should be around 20 to 80 or so. (ballpark) Most of these boxes had SSB delays in them. As I said , they were not the best built and they could be down right dirty , but they worked and they would sound very nicely when driven correctly.

The Marko's were usually a single powered units. This one is a Marko 100 F (about 20 years old) 2 x 454s (80 x 2) SSB delay Class C , this one likes a 1 watt DK this amp amp gives about a 75 watt DK to 160 watt pep swing.