.............a worker bee at the Pentagon would have never though of it that way.

A frequency modulated carrier changes frequency in step with the audio... The deviation (frequency delta) from the nominal frequency is 5 kHz for 2 Meter FM which is adequate for communications grade audio. Your local FM broadcast stations are spaced 200 kHz apart and allowed a maximum of 150 kHz deviation. Old school NTSC TV ran AM modulation on the video and FM audio at 50 kHz deviation.

From what I gather in this thread the greater the [D]eviation (frequency swing) the better the high frequency response in the [M]odulated audio. You know this is true because FM broadcast sounds way better than your local repeater.

Next time you're visiting your local big box handy guy store stroll through the paint department with an eye open for Jasco rust prep & primer. White plastic bottle about a foot high. It's essentially phosphoric acid and as the label will tell you it stops rust by chemically transforming it into a stable black coating that's allegedly a primo primer. Same concept as Naval Jelly.

This won't do squat for the copper cladding but it will snuff the rust bunnies. Think in terms of neutralizing, sanding, then paint or plating to make the chassis Drakeworthy again. This is not a quick & dirty fix, although a little patience and a brass bristle brush can turn the worst of it into a memory...........

BTW:  As nice as a copper chassis can be, nothin' beat the high end pre-war E.H. Scott chrome chassis models. We're talking industrial art at its finest...

If you're clever enough to add a ratio detector to the butt end of the last IF 'can' it could learn to do FM...........

I have a feeling the last IF 'can' (as you would call it) isn't at the now standard 10.7 MC, although the AM detector 'can' might have enough of a secondary winding to be adapted. If you're looking to keep it authentic, nose around your Phabulous Phifties Beitme squidmatic books for AM / FM schizmatics to see how it was done back in the day.

Typical FM detector used a 6AL5.   YMMV.   I don't see much value in an AM / FM mod as there are only three Hams in New Jersey who are still interested in Two Meter AM and four of them are in a nursing home.  One of 'em is a little schizo........   

Here's a Thot:

The DC voltage will go high when there's no load to pull it down to a safer value. There is a fairly simple way to add a voltage selective load that you can research under the name "Shunt Regulator". Imagine a 14 volt Zener diode of the stud mount variety on a small heat sink in series with a 10 Watt resistor of maybe 100 Ohms or so. You know what you're working with better than I do, so work the numbers and you'll get handy with Ohms law as a bonus.

Basic concept is to wire the Zener and resistor in series. Then connect the combo across the DC power leads. If the voltage climbs above 14 the Zener begins to conduct and the resistor becomes a partial load. This will waste some juice, but only at times when you have more than you'd like. When you turn on a radio or other load device the line voltage could drop enough for the Zener to become almost transparent so you won't be wasting power when you want power. If you're a clever bunny you might even find a magic value for the resistor so you can add an LED to tell you when it's working.

How cool would that be?

Should be an easy and inexpensive project that won't cost too much extra to overbuild..................

So............. You're saying the woman in the 1938 film clip might be talking to Ed Wynn, or that cocoanuts are migratory?

The two transmitters should be interchangeable unless you're loading to an oddball impedance through the tuner. If you have a 50 Ohm dummy load, connect it directly to either transmitter and adjust the Pi network for best match. Do the same to the other transmitter. Connect the tuner and adjust it for best match without changing anything on the transmitter.

At this point you should be able to swap transmitters without any issues as they're both set to a common impedance.

If you can't get a match to the antenna without tweaking the transmitter that tells me you're compensating for an antenna system that's well outside the range of the tuner. Back in the day a Pi network usually had enough range to match a close-but-not-perfect antenna system without a tuner, and that was the preferred setup.........

( ? )

Excellent Twilight Zone this past Friday night..........

Hipster wise guy 60's kinda' guy buys the farm and ends up in heaven. Must be heaven because every bet he takes pays off, wins every game he plays, and every babe he hits on comes across for him. Guy can't lose no matter what. After a week it starts to get on his nerves because always winning is worse than always losing. There's nothing stopping you from repeating the same play that brings you no joy any more. At least when you're losing you run out of money and have to stop. With perpetual winning it's pointless to play, but you do, with hope that maybe this time will be different.

After a month he tells his handler (played by Sebastian Cabot) he can't stand heaven and really deserves to go to the other place.

Handler says:  You think you're in heaven?  Sir... YOU ARE IN THE OTHER PLACE AND CAN'T LEAVE !

I saw it coming, but it was still way cool.

I think the hunch is that you're inducing enough power from the AM BCB station to fake out out the transmitter SWR foldback protection circuit. Remember that with a poor SWR a portion of the TX power is reflected back down the feedline and the SWR meter doesn't care if that voltage is on 1340 kHz or the DX Window of 20. The big clue for me is that this only happens when the AM station is at full power.

I'm going to guess that you're using a large-ish dipole cut for one of the lower bands as a triband beam is mostly deaf on the ol' AM BCB. Ferrites on the coax can help if it's a common mode issue (antenna + feedline = longwire) but if it's a case of an all-band Doublet that really likes talk radio the cure will be a smaller antenna, a high pass filter, or a tuned stub on the feedline.

Hang your DC voltmeter on the AGC line and measure the voltage with a moderately strong station tuned in. Tune to a quiet spot on the same band and note the AGC voltage with that condition. This will tell you in which direction the voltage swings for strong signals and weak signals.

Switch to the band that's dead and do the same. Betcha' the AGC thinks Radio Habana is next door and it needs to go deaf.

Figure out why.

Found this linked on the Coast To Coast AM web site...  http://www.youtube.com/watch?feature=player_embedded&v=9Ra6EopXf1w#!

Allegedly a film clip shot in 1938 showing what could be a time traveler having a chat on a cell phone.

Yokay, let's go with that.  It's 1938.  Where's the cell tower?  What's her account number?  One?  Two?  Unlimited data / texting or just talk time?  Then there's the question of who she's talking to........ Another time traveler in 1938 - or - someone in 2008 with the Dr. Who Ultimate Roaming package?

Point being that it takes more than a cell phone to make a call on a cell phone.

Unless...............   You're calling from...............   The Twilight Zone.

.

If you want technical detail, this should scratch your itch:  http://www.g3ynh.info/atu/collins180L.html


1957.  Whooda' Thot?  And how cool is that ribbon inductor............... ?