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Author Topic: A piece of Radio History and a weird little circuit to get it done!  (Read 9253 times)
N9MXY
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Posts: 240




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« Reply #15 on: May 16, 2013, 05:00:24 PM »


Quote
How do you know it's "FCC accepted?"

Today, an amplifier of any kind with those characteristics (frequency range, RF keyed, can be driven with 5W) cannot be certificated even if one stood on his head and juggled. Wink

Does it have an FCC file number on a label or something?


 Yes Steve it does have a label right on the amp!  That is a big part of what got me interested in it in the first place.

 
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W9GB
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Posts: 2652




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« Reply #16 on: May 16, 2013, 05:43:55 PM »

Quote from: N9MXY
Kinda a strange duck and I stole it on Ebay so I think I'll just stick it in the closet for now for a conversation piece....
Carl -

I spotted that item on eBay earlier, but did not mark or watch it.  Now I know who got it!

I seem to remember another mfg.(Sonar BR-21) in early 1960s producing an amplifier that looked like this Pace unit.  BR for Business radio.  1950s LMR did have 25 to 27 MHz allocation, in addition to the Low Band VHF LMR allocation above 30 MHz.
http://www.cbtricks.com/Amp/sonar/br21/graphics/sonar_br21_cover.pdf

Many CBers and radio amateurs have forgotten that the number of CB licenses issued equaled the radio amateur licenses issued by mid-1960s.

In that period, vacuum tube Citizens Band, Class D radios (mobile & base) were an inexpensive alternative to Land Mobile Radios (Part 90) for small buinesses, such as taxi services, school districts, bus companies, cement companies, construction companies, etc.  EF Johnson Messengers were very popular in 1960s.

Consumer operators did not appear until early 1970s with the first solid-state CB radios appeared.  
The CB craze started after the 1973 Arab Oil Embargo, when finding an open gas station on longer trips was important.  This was then followed by national 55-mph speed limit and 1979 Iranian revolution (second Oil embargo).
« Last Edit: May 16, 2013, 05:52:36 PM by W9GB » Logged
K8AXW
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Posts: 3958




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« Reply #17 on: May 16, 2013, 08:11:53 PM »

Pace was a maker of CB equipment..... usually pretty good equipment.  I owned two Pace CB transceivers....a base and a mobile.  I still own a Pace SWR/Power meter.

The amp shown is a CB amplifier and it has to be biased in the linear region of the PA transistors in order for it to amplify an AM CB signal with any kind of linearity at all.

Unless I missed the PA transistor voltage and conduction curve charts someplace, you can't tell what the bias is.

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N9MXY
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Posts: 240




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« Reply #18 on: May 17, 2013, 03:46:09 AM »

Thanks for the input guys!  I figure this thing is a pretty early effort in what was then high power transistor amplification, very early 70's, maybe even late 60's.  I am surprised that still it works at all and this one seems unmolested. I downloaded the manual and it has a FET preamp with 2 adjustable inductors to fine tune the input and output matching of the preamp. It's really a pretty interesting little piece.
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WB2WIK
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Posts: 20633




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« Reply #19 on: May 17, 2013, 10:43:51 AM »


Quote
How do you know it's "FCC accepted?"

Today, an amplifier of any kind with those characteristics (frequency range, RF keyed, can be driven with 5W) cannot be certificated even if one stood on his head and juggled. Wink

Does it have an FCC file number on a label or something?


 Yes Steve it does have a label right on the amp!  That is a big part of what got me interested in it in the first place.

 

It would be expired or invalidated today; however, it would be interesting to know what the registration number on that label is, so we could attempt to look it up.

Any FCC certification label should always carry the number on the label.
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N9MXY
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Posts: 240




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« Reply #20 on: May 20, 2013, 03:44:03 AM »

http://smg.photobucket.com/user/hitechluddite/media/FCC.jpg.html

Steve, It's just the model# I guess PX 200 BL
« Last Edit: May 20, 2013, 03:55:49 AM by N9MXY » Logged
K0KUZ
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Posts: 4




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« Reply #21 on: May 20, 2013, 10:09:09 AM »

Come on gang, where is the love?Huh

don
K0KUZ
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KB1GMX
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Posts: 811




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« Reply #22 on: May 20, 2013, 03:52:12 PM »


If its the one i remember it comes from the same era (pre 40ch CB) when 27.235, .265 and
a few other channels were designated as Business CB and carried a slightly different license. 
At that time a Courier BL-100, ML100, Lafeyette had a similar amp, to name a few they were
100W input class AB or AB1 using sweep tubes (6js6 and friends) and for AM ran about
25-30W carrier with clean peaks. There were a few solid state amps and they generally ran
about 75-100W input and were biased for about .2 to as high as .6A no carrier
(single ended and push pull) for linearity.  Most were very clean though the devices of
the time were fragile.

AM and SSB both require a linear amp, only FM and CW can run Class C (back then).

Oh, and there was a lot of crap out there mostly CB rigswith type approved stickers
that were real.  One that came to mind was some of the cheaper radios.  Different
standards then as the 40CH era were also compliant to new standards for
signal cleanliness and adherence to power limits and also the ban on amps that
work above 15 and below 30.

I know this as back then I used my 1st class to cert my brothers commercial setup (legitimate
use for business).  CB wasn't always wild and woolly, and we aren't talking the same thing as now.   
Back then you could be busted for being dirty.  Though there was a lot of angst between CBers
and hams as it wasn't that long before the hams lost 11M.  Despite that there were a lot of hams
that were also legal CBers with calls.


Allison
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K1ZJH
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Posts: 1140




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« Reply #23 on: May 20, 2013, 06:25:52 PM »

Guys, here is the schematic for the amp...

http://www.cbtricks.com/Amp/pace/px200_bl/graphics/pace_px200_bl_om.pdf

Please not that all three finals are in parallel, and that the bases are returned to ground via 0.82uH choke. There is no forward biasing on the finals, and they are not being run linear. The manual spec's AM or FM operation. It was very common for early CB AM amps to be run close to Class C. The IMD was horrendous, but they sounded okay on channel.

Pete
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SWL2002
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Posts: 374




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« Reply #24 on: May 21, 2013, 03:37:33 AM »

Guys, here is the schematic for the amp...

http://www.cbtricks.com/Amp/pace/px200_bl/graphics/pace_px200_bl_om.pdf

Please not that all three finals are in parallel, and that the bases are returned to ground via 0.82uH choke. There is no forward biasing on the finals, and they are not being run linear. The manual spec's AM or FM operation. It was very common for early CB AM amps to be run close to Class C. The IMD was horrendous, but they sounded okay on channel.

Pete

You are wasting your breath.  I pointed this out earlier in this thread (even posted the same link to the schematic that you did), but it fell on deaf ears.

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N9MXY
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Posts: 240




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« Reply #25 on: May 21, 2013, 05:51:39 PM »

There's no forward bias so maybe it's open ended class A and it's really an audio amp! Smiley
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