I had one of my L4B's apart yesterday.

The plate choke measures 157.34 uh.

Hooked up to the VNA, it series resonates at 16.464 mhz.......and also 23.373 mhz.? ?On paper, the choke should work on 160-10m, including warc bands.

Hello!

I have been restoring a Drake L4-b for the past year or so. However, my amp is not making power, and there's no grid current. Since it's been a while and I didn't take notes, I'll do my best to remember everything I've done.

I had one of my L4B's apart yesterday.?

The plate choke measures 157.34 uh.?

Hooked up to the VNA, it series resonates at 16.464 mhz.......and also 23.373 mhz.? ?On paper, the choke should work on 160-10m, including warc bands.?

?

The ceramic it's wound on is 5.0" tall......(x 1" diameter)....then the machine screw above that.? ?The Ameritron 3 x section choke is 5.5" tall ...x 1" diameter....then the machine screw above that.

The lid can be down, with the Ameritron choke in there, but it's too close to the top lid.? There is not much of a gap. A small square sheet of Teflon on the underside of the top lid might work.

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I just finished winding? several? hb? ferrite loaded chokes recently.? ?They ranged from 762 uh down as low as 304 uh.? ?These consist of shimmed, type 61 ferrite beads slid down the inside of some hollow teflon tubing. (1" OD x? .710"? ID? x .145" wall thickness.?

To hold the hb choke to the chassis, I used a 1" ID electrolytic capacitor bracket.? 1/2" or 3/4" copper strap is wrapped around the teflon tubing, ( top and? bottom) and pinched off with a single brass machine screw, and brass hardware.? The winding at each end terminates on the copper strap.? I used 22 ga, Belden silver plated and stranded wire to wind the chokes.? This stuff is .060" OD....and the? Teflon is thickwall....at .016" wall thickness.? ?I also have 22 ga teflon silver plated, stranded wire that is only .044" OD...and has a smaller, .008" teflon wall thickness on the insulation.?

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If required I could easily fabricate a plate choke for the L4B that would suffice, and not series? resonate anywhere from 1.8-30 mhz...and fit in the oem cabinet...with plenty of clearance.??

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So far, so good.? I tested them in the VNA....and they have to be away from metal....and also dielectrics... otherwise, both series resonant freqs will drop a bit, like 500 khz.....fine, as long as you factor that effect in.? ? Also tested em with 3.22 amps CCS of DC flowing through em for 2 hrs. The inductance dropped by 2-3 uh.? Series resonance freqs shifted upwards by a tiny bit.? The hottest point on the winding was 117F.? The hottest the beads got inside was 90F.?

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On the hb amplifiers, there is a 1/4" hole drilled below the choke, so air from the plenum flows up through the entire choke.? If required, the hole could be reamed out to? 3/8"....(since the beads have a .374 ID).?

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Type 61 was used, since U1 and U2 cross at exactly 45 mhz.? The Q of the material drops to almost zero where they cross.? (type 43 crosses at exactly 7.0 mhz).? ?Resistivity of type 61 is a full magnitude higher vs type 43,33,31,77,75 etc.? ?Type 61 is 100 megohm per CM.? Currie temp is a lot higher too.? Still, type 43 has been used successfully on other amplifiers.?

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The latest pair of chokes I cooked up, are 397 uh....and also 416 uh. They are hand tweaked to series resonate exactly where I want them....( 17.675 mhz...and also 16.209 mhz.? ?Both are made for a specific application. (160-80-40-20-15m............ and 160-80-40-20-17-15m.?

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Yesterdays net was held on 7.238?@ 4pm Eastern. We had a total of 27 check-ins. The following list of radio's were used:

I did not see the referral for that articl

would the newer metal oxide film resistors rated at 5 watts be a better replacement for the old carbon resistors?? I am looking at replacing the 47 ohm carbon 2 watt resistors in my L7 with 47 ohm 5 watt mof resistors.

ALC was never intended to be a speech processing system. Undesirable things happen when you try to do that. I point (again) to SM5BSZ's work in this.



73

-Jim

##? read it several times, eons ago.? I have two FT-1000D's.? Basically, before u turn the RF clipper on,? you 1st adjust the mic gain for XXX? alc action.? ?Trying to maintain XXX? alc action requires an outboard audio compressor...to maintain a constant audio level going into the xcvr.? Otherwise, clipping level will be a function of how loud u talk.? ?Then with clipper on, dial up XXX db of rf clipping.? Note, the analog meter in the FT-1000D reads average, not peak, so when the meter sez.... '10 db clipping'? it's actually 20 db of rf clipping.? (The analog meter only reads peaks when on RX, that's it).? So along comes joe ham, tweaks the clipper for 15-20 db of clipping, then ends up with 30-40 db of clipping.? Manual sez no more than 10 db of clipping, as indicated on the average reading meter ( which is actually 20 db of clipping)

## once RF clipping level is tweaked, meter is switched back to read ALC.? ?Then the OUTPUT control is tweaked so that you have the same ALC action, or less....than you had with clipper off.? ?With a quality (IE: rack mount pro-audio, professional audio compressor) feeding the xcvr, and clipper on, the output control on the yaesu can be tweaked for very little alc action, just a miniscule amount is required.? ?At that point, you can have all the clipping you want, with minimal output alc action...and no alc artifacts.??

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## old guy north of me, had a FT-1000D, and never did get it through his head how to adjust the clipper.? He would have the clipper on, see the alc was on the low side, then proceed to crank up the mic gain...which is exactly what u don't want to do.? By turning up the mic gain, the clipping level just went way up. What he shoulda been doing is to tweak the clipper output control, to adjust the alc.? ?I showed him several times...then gave up.?

I experimented with my 6 x band digital compressor,

*** Is that something you bought? Or something you made?
I've played with audio with a PJRC Teensy 4. They have an audio
design tool on their website; you drag and drop mixers, filters etc,
and it creates a skeleton "C" program to implement it.

I used that to create a CW filter/translator for my KWM-2, which
is horrible for CW as is - because the sidetone & received signal are
1750Hz. I mix it down to 650Hz and do some serious audio filtering.
All in software.

- Jerry, KF6VB

##? Nope.? I bought a behringer 9024? 6 x band digital compressor.? Rack mount. I had 3 of em at one point.? The 6 x bands are nose to tail, no gaps....and a max of 20 hz to 20 khz.?

For ham radio use, essb, etc, the 6 x bands are typ programmed for aprx 50-200 hz, 200-800 hz, 800-1600 hz, 1600-3000 hz, 3000-4500 hz, 4500-6000 hz.? ( Or any combo u want, but u gotta use up all 6 x bands).? Each band has separate compressor controls, each has it's own noise gate etc.? You could spend months and months playing with it.

##? to get any of it sounding correctly, u 1st have to do some serious eq'ing.?

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"Note that as a rule of thumb the ratio of peak to average in male speech is about 10db."

Most tech literature indicates 14.5 db.? Other literature indicates 21.5 db.? ?They call that crest factor.? ( peak to average ratio).

Point is, without basic ALC, your average power output on SSB would be through the floor.? ?That's assuming using just enough audio drive to? just drive the xcvr to say 100w pep out.? ?You can see that on any average reading wattmeter.
if u want true average, use an RF ammeter.

Got the new 10 turn pots installed and wow what a difference!? ?Got a dumb question - WB4HFN says in his "Identifying the Drake TR7 Transceiver" to use the 1K resistor at the top right of the power supply board as the test point to set 10 volts.? The service manual says to use the 10 volt trace on the parent board.? Does it make any difference which one is used?

73, Bill NZ0T