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RCI69 base. Has RCI finally jumped the shark?

nomadradio

Analog Retentive
Apr 3, 2005
6,935
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Louisville, KY
www.nomadradio.com
So here's a question. Has RCI finally jumped the shark?

Here's what the latest "Black Radio" from RCI looks like on the outside. Yeah, a poorly-posed pic. Had more important stuff on the plate that day.

6da19n.jpg


Didn't get a lot of other shots before it had to go back together and go home.

I did get this one. Leads me to the subject of my discontent. This radio sounds like poo on sideband transmit.

Here's why, best I can tell. Too much gain packed too tightly together.

BdjZbU.jpg


The nasty sound of sideband transmit comes from RF feedback between the final stage and the low-power stages. Until this model, RCI radios had a tiny transistor buffer, followed by a small pre-driver (no heat sink) feeding the actual driver transistor, feeding into two parallel driver transistors.

This thing has a driver transistor feeding into the driver transistor.

In effect.

Took me almost two months to get this posted. I'm curious what experience other folks have had with this new model.

My idiot light is still glowing from when I realized I didn't write down or get a pic of the circuit-board's "EPT" type number.

Was a busy week at the end of December.

For now I'm not recommending this radio for sideband until I see a convincing way to make them stable.

Yeah, that's kinda presumptive, based on experience with exactly one specimen.

And if I never see another one again, that could be a clue all by itself.

73
 
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Not to mention that RT-1 "final" is some kin of a transistor used in a power supply if I remember right.
 
Smoking Joes Electronics did up a Vid on the brother to this - it's Chromed cousin...
RCI69VHP

But there was a thread or two earlier...found one that showed the spectral rainbow of channels - er - harmonics...o_O

https://www.worldwidedx.com/threads/rci-69-base.253568/

Both chassis use the 12D version - so your photos and their board - well, I guess we could call it a match...

One thing though, I still have to ask, what did they ever do for "X"? (That missing part?)

That may be part of this problem...no turning down the output - because of no feedback being used can easily overdrive the following stages...
 
I think I am encountering this ssb issue with my new rci 69vhp mobile. If I turn the internal ssb power adjustment over about 30 watts the unit goes into oscilation. Ssb does sound pretty good at the lower levels.
My unit may need to go in for waranty service, unfortunatley the waranty card was not included with my unit. The owners manual says waranty info is in back cover of manual.
 
Thanks. I will give them a call monday, maybe they can tell me what to do, other than that issue the radio is great and gets good reports on am and ssb using a stryker noise canceling mic. The stryker mic feels cheaper than the stock president mic but matches my voice better than the sra198 or the 636.

It may be that this radio just needs to be run below advertized specs to turn a hot rod into a daily driver.
 
That's likely why Qixiang has the metal plate and thermal pad over the front of the devices in the Stryker and Anytone.
A lot of amplifier designs that employ MOSFETs also have an aluminum bar across the front of the devices to clamp them down and provide another path for heat.
Maybe the metal plate also acts as sheilding to prevent feedback/oscilation issues. Should have coppied that part too Ranger.
 
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I lost a final yesterday on the dummy load while demonstrating the issue to my boss. Waranty service is six weeks out so I thought I would do a little investigating for the good of others and the 690012d board.

Best to set final bias first, before the driver can "leak" any carrier and skew the final reading. So long as the Vth of the two finals are a close match, this is probably good enough. But never dare to put two unmatched finals into this radio. Like playing russian roulette but with five chambers full and only one empty. Too many chances to be a winner.
The test results of the 3 surviving rt1s are:
Final C 749 vt 3.4
Driver C 720 vt3.1
pre driver C 734 vt 3.1

I had a longhorn n6 on the bench last week that had a blown rt1 in the radio final section. The test result for the surviving rt1 out of the longhorn:
c727 vt 3.1
 
I really believe 520's are a better alternative in these rt1 using rigs. Yeah you lose a little power but gain longevity.
It's been an issue since the beginning of the rt1 (irfz24npbf) being used in the rangers, and worse that they continue to build the radio's with them.
I own an x9 with those in the final section and it's not a matter of if they fail but when they fail.
 
I used a pair of irfz24n in my lincoln 2 for a year, volted and they held up well. I think the matching is key.

Also the finals in this radio run at line voltage so if you Bias at 13.8 does the bias change at 14.5 vehicle voltage?
 
I used a pair of irfz24n in my lincoln 2 for a year, volted and they held up well. I think the matching is key.

Also the finals in this radio run at line voltage so if you Bias at 13.8 does the bias change at 14.5 vehicle voltage?
Hmmm good question. So for testing purposes, adjust bias on the test bench with a 13.8 voltage. After it's set, turn the voltage up on the power supply then check bias again as see the results. So this is just me thinking (I'm no technician), wouldn't the voltage be stabilized by the regulator so that it remains the same? Is my understanding incorrect? I understand a higher provided by the voltage source would just prevent voltage and amperage drop.
I'm opened to learning
 
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I picked up a couple sleeves of IRF520N's from
Hmmm good question. So for testing purposes, adjust bias on the test bench with a 13.8 voltage. After it's set, turn the voltage up on the power supply then check bias again as see the results. So this is just me thinking (I'm no technician), wouldn't the voltage be stabilized by the regulator so that it remains the same? Is my understanding incorrect? I understand a higher provided by the voltage source would just prevent voltage and amperage drop.
I'm opened to learning
It shouldn't matter what the source voltage is. Take a look at this chart (from the IRF520).
2023-06-27 15_06_33-irf520 new order.pdf - Adobe Acrobat Pro.png
Check out the bottom curve (the one with the lowest Vgs of 4.5v, closest to what the radio is biased at) and how it holds a constant drain current once the Vds is above 1v. This means that once you have your bias current set (which is controlled by a regulator), the drain current will not change even if the drain voltage does.

Be sure to set final bias by drain current, not gate voltage like some sources say (edit: A spectrum analyzer does it best though!)
 

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