linear....really?????

[redbeast]

A buddy of mine just gave me this linear(?) and an rk56. Havent opened it up yet to check......look familiar to anyone? Any ideas as to what the preamp switch is for? Looks like a cobra power plug. Illl open it and send more pics later.

 

[Robb]

Doesn't look familiar. But if you post some pictures of the inside and copy the numbers off of the two main transistors (aka 'pills'), it will be easier to tell you more about it.

An original RK-56? Or is it a newer version? Big difference. The older version is quite desirable to use, but the new ones will work OK too.

 

[LeapFrog]

Any ideas as to what the preamp switch is for?

The switch is going to be for the receive amplifier also called a preamp, this helps to amplify the received signal.
Depending on the preamp design used, the white noise or static can become amplified to a much greater degree than the signal of the distant station you are trying to hear, the cheap pre amps have this problem, a decent pre amp will have a much better signal to noise ratio than the basic ones. (White noise/static compared to signal)

These can be helpful for long-distance communications (when you have a low gain antenna) or when conditions are not ideal.

I have an older RK-56, it is one of the best microphones I own.

-LeapFrog

 

[Pappas and Beer]

Yes, it is a Palomar Elite 300 without the label. I would bet it was made by the late great Vernon out of Texas sometime during the late 1990's or early 2000's. It has 2 1446 transistors in it. It may have "automatic SSB" It was made by "Native Americans" whom Vern hired, and they eventually went on strike when he would not let them take off work on "Native American Celebration Day". (Ironically, Vern was at least half Native American). His son (or son-in-law?) begged him to let them take off work, but he was too stuborn. He never recovered from that. He was probably about 85 years old when he made that amp. I believe he died when he was 93? Notice the similarities in the pics here:
[photo="medium"]4359[/photo] [photo="medium"]4323[/photo]

 

[LeapFrog]

Yes, it is a Palomar Elite 300 without the label. I would bet it was made by the late great Vernon out of Texas sometime during the late 1990's or early 2000's. It has 2 2sd1446 transistors in it. Notice the similarities in the pics here:
[photo="medium"]4359[/photo] [photo="medium"]4323[/photo]

Not trying to be nit-picky here, because you may be 100% correct, but I notice a gap in the middle of the heatsink on OP's amp, and it doesn't have the mounting flanges either.
The low-medium-high switch is missing also, could still be a 300 elite on the inside!

We need internal pictures to really indientify this box.

 

[Pappas and Beer]

I can tell Verns work. The screws, the way the aluminum cover slides on, the lettering on the back is a give away- it is exactly the same font! The black plastic thing where the power wires come out, look like from the same manufacturer. Those always would come loose. The pics I posted are circa 2008. The OP's amp is around 10 years older. We need an internal pic. I was wrong once, you know.

Here is the inside of the Palomar Elite I posted:
[photo="medium"]4367[/photo]

 

[Pappas and Beer]

Here is one of Vern's best, the Palomar 700. He always liked the 1446 as drivers because "they have more swing". Can we get an internal shot from the OP?
[photo="medium"]4368[/photo]

 

[redbeast]

Here is one of Vern's best, the Palomar 700. He always liked the 1446 as drivers because "they have more swing". Can we get an internal shot from the OP?
[photo="medium"]4368[/photo]

Yeah, Ill try and get to it toute sweet, just got home from work, and Im beat. Looks to mee like the board slides out from the end...one piece case/heatsink? The timeframe that P&B was talking would be about right according to the info i got from my buddy. Never seen a linear this small before, looks like the bracket screwed right on to the radio case. More to come

 

[redbeast]

Yeah, couldnt wait. 4 screws, move the front, cover slides off. Looks like 2"pills" jumpered. SD1446, 59V, 0130; no signs of corrosion or burning. Couldnt find #s or marks on the pills. Hope the pics come through ok.

 

[Robb]

The single SD1446 transistor means that the output would be around ~80w peak power.
Pics are good enough.

Usually, these amps come with two transistors. This kind of single transistor amp usually is used to drive a much larger amp. But it should work fine - as is

 

[LeapFrog]

Yup if it works, you now have a "1 pill driver".
Like Robb said these are usually used to drive large amplifiers, some people like to run a one or two transistor amplifier in a mobile environment because they will not demand serious current like the big boxes do.

I will have to check the data sheet for an input rating on that transistor, also does anyone spot any attenuation on the input?

I like the colors on that circuit board, to me it says "made in the days before most things became made in China."

I can tell Verns work. The screws, the way the aluminum cover slides on, the lettering on the back is a give away- it is exactly the same font! The black plastic thing where the power wires come out, look like from the same manufacturer. Those always would come loose. The pics I posted are circa 2008. The OP's amp is around 10 years older. We need an internal pic. I was wrong once, you know.

Here is the inside of the Palomar Elite I posted:
[photo="medium"]4367[/photo]

@ Pappas and beer, not to get sidetracked here, but did this Vern fella re-do these Chinese amps, the board pictured clearly has "Made in China" printed on it, what self respecting builder would want that associated with their name?

I could see if he upgraded several components, and the entire amp all the way around.
Was he the guy that is so good he made China amps last & perform like American steel?

 

[222DBFL]

Also I think he stated is was a 2 transistor amp with the transistors jumpered. How is the amp setup redbeast?? I know you said 2 pills jumpered. Could you explain more??? Or take a pic of how the amp goes together. Hard to tell by the pics that it's a 2 transistor amp is what I am saying I suppose. Thanks for any replies. And that site doesn't look like my Palomar knockoff. It's only a 200 watt amp. More like 150-200 watts max pep on SSB. Like Robb said, about 80 watts per transistor depending on the voltage being fed to them. And I don't mean using too high a voltage. 13.8vdc-14.2vdc being max voltage. Anyhow. It maybe like mine but it just doesn't appear to be. My switches are, pre amp, AM/SSB, and a H,M,L for the power settings. 3 red leds and a black case that had 250 on it and also says class AB bias. Like the others have said, is it's not broke don't mess with it!! And don't overdrive it. About 2 watts dead key and 8 watts on AM and about 12-15 watts on SSB is plenty to make it work as intended. JMHO's. Have a good one.

 

[LeapFrog]

6 watts p.e.p. max Is about what I would start with for a test, that's "max forward swing power" or "100% modulated carrier" so a 1.5 dead key, now that I'm sitting here typing this out I would start with half a watt carrier and slowly drive it up if your radio has a variable rf power or a variable dead key mod installed, if you're just gonna be running a capacitor & resister mod in a cobra it's gonna be much more difficult to get the correct drive levels into that amplifier and the radio will overmodulate with that modification without some serious effort in the tune done to prevent the "swing kit audio"..
Most of the capacitor/ resister modded Cobras look like absolute garbage on the 'scope, and I would never think about running them into a power amplifier. Though with some effort I was able to get a semi-clean result using a TIP120 transistor for the variable deadkey.

If this amplifier indeed has only one transistor you would be driving the crap out of it, if you ran it with the input intended for a 2 transistor model.
Here is the Datatasheet.

Robb (or anyone) if I'm reading this datasheet correctly, about 7 watts in equals 70 watts out @ 30Mhz?
8 W would be over driving it at the intended frequency range, if it is a single "pill"/transistor amp that is.

I don't think you would have any problems running 1 W dead key into this box, to avoid over modulation and splatter the radio should ideally be tuned for 90-100% modulation and no more, this would equal four pep watts from a 1 watt carrier (dead key).

If the output is too low for your test conditions you could slowly raise up the carrier, maybe up to 1.5, then 2 watts.

I have tested a small linear that can do 75 Watts of average power from less than four watts of input, but I still only run 0.5 watts into the amplifier and let it swing to 2 Watts, It did not over modulate and sounded crystal clear during my bench test.

The input drive that your amplifier wants to see is a factor of what type of device is used in it, how many of those devices are used, and if there is a driver section inside the amplifier or any input attenuation.

Let's say If you have a four transistor amplifier ( & they're all the same series of transistors) if an individual "pill" calls for one watt of input, it is then safe to assume that the four transistor amplifier would be fine with a four watt input.
[ this is a very generalized statement for illustrative purposes ]

As always you must be aware of your country/local residents regulations governing the use of (rf) power amplifiers and communications. How often these regulations are enforced is a moot point, because they are enforced.

 

[Pappas and Beer]

Yup if it works, you now have a "1 pill driver".
Like Robb said these are usually used to drive large amplifiers, some people like to run a one or two transistor amplifier in a mobile environment because they will not demand serious current like the big boxes do.

I will have to check the data sheet for an input rating on that transistor, also does anyone spot any attenuation on the input?

I like the colors on that circuit board, to me it says "made in the days before most things became made in China."



@ Pappas and beer, not to get sidetracked here, but did this Vern fella re-do these Chinese amps, the board pictured clearly has "Made in China" printed on it, what self respecting builder would want that associated with their name?

I could see if he upgraded several components, and the entire amp all the way around.
Was he the guy that is so good he made China amps last & perform like American steel?

Vern was was an old man and didn't care what people thought about him. That was the pre-Trump era when China stuff was still cool. He just enjoyed making inexpensive amps and selling them.

 

[LeapFrog]

Vern was was an old man and didn't care what people thought about him. That was the pre-Trump era when China stuff was still cool. He just enjoyed making inexpensive amps and selling them.

Sounds like a very good man, it's a shame he is a silent key now.

73