Amplifier

[kk4fpx]

I'm posting this on CB because I bought a Palamar TX-150 amp to use on 10 meters.They were meant for CB.I can't find a user manual for it.
Anyone know anything about this amp?

[KA9MOT]

I know enough about it to tell you that it is garbage. This amp is not suitable to be used on 10M unless you have allot of skill building amplifiers... and it won't be easy to clean it up.

[KG4CGC]

Tap the coil by 1 loop shorter. If you put a clean signal in, you'll get a clean signal out. Most of the trash you hear about these things is based on guys running a wide, over modulated, over powered signal through them to begin with.

[kk4fpx]

Well so far it seems to be doing the job.I got very good reports from Brazil and California so far.It's pretty broad banded 26 Mhz to 54 Mhz from what I can find out.I found the spec's on the tube model but not this one.It's designed for 4 watts in but I'm running 5 watts on my HTX-100,can't use the 10 because it 25 watts only.
I'd sure like to find the user's manual.I'm pretty sure I'm useing it right.I had to buy a 35 amp power supply for it,I only had a 12 amp one.I got a good deal on both at the Gadsden Ham Fest this morning.

[kb2vxa]

Don't tell anybody but I had something very similar a long time ago in a galaxy far away, nice clean signal and praise instead of bad reports. Just a simple, straightforward two transistor push-pull amp with a one transistor RX preamp and the usual RF sniffer relay control. Using an amp makes using a monitor scope all the more important, those CB amps are easily driven into Class C which seems to be the aim of those Chicken Band Outlaws that have given otherwise perfectly good amps a bad name. Palomar had a long trusted reputation for quality until it went out of business in 1980 unlike Dave Made or Texas Star junk.

[WØTKX]

True dat. Don't over drive the driver. They work OK. I poked around on the net, info is available for a price.

[NQ6U]

Palomar is a local company, based in Escondido. They don't build amps any more but they're still in business selling ferrite toroids and a nice (if pricey) kit for dealing with RFI issues.

[KA9MOT]

I might be off in my opinion. It may be OK on 10M. I wouldn't bet my ticket on it.

[N8YX]

Believe it or not, you may already be using a PA of that nature in your older U.S.-built amateur/commercial HF radio!

The circuit in question was used by Swan/Cubic and Ten-Tec - a modified version was used by Heathkit. I'm talking about the venerable 100/140w output (class AB/C) 2x MRF455/458 design which essentially was copied straight from Motorola's Application Notes.

There are provisos and caveats involved:

1) No low-pass filtering on the output assumes a very pure (band/low-pass filtered) input;

2) You must pay attention to biasing (particularly, in the area of thermal compensation) and drive levels.

3) Many CB amps of the day which used the design used RF output transformers that were simply not large enough for the task at hand and can easily be driven into core saturation.

Best way to use this amp is to construct a low-pass filter for both input and output, keep the drive down (use an input padder if necessary) and verify that the correct biasing scheme is in use. Most non-amateur market amps of the type don't have it, but if one studies the appropriate Application Notes one finds it's not that big of a deal to modify the existing design. Another thing I would recommend doing is looking into adding negative feedback by means of degenerative emitter swamping resistors - it'll prevent the transistors from going into oscillation at VHF in certain drive regimes.

All this info is readily available - either online, in a Radio Amateur's Handbook from the late 70s or from an older Motorola RF Power Devices book.

[PA5COR]

Most of these amps lack a bandpass filter as is obvious since it works over a very wide range without having to set the band switch, leaving all spurious a path to the antenna.

Also their bias circuit mostly leaves a lot to desire, i rebuild many of these amps, still have a KL 500 amp here as new that needs input and output bandpass filters and reworking the bias for the 4 MRF 455 transistors.

RF sniffer rx/tx switching bypassed to hard wire switching needs to be done as well.
I did a few of these and they can make 300-400 watts clean after reworking, not the 500-600 RM Italy claimed watts....
Good for prepping up 10-20 watt transceivers for a bit more output.
But then i have the Heathkit SB-1000 with new 3-500 ZG in it so i don't need them, i mostly sell them off when finished to hams here.
Add a few temperature controled fans on top as well.

They are basically the Motorola EB 104 design, from the Motorola transistor handbook i have sincee 30 years or so.