High capacitance per foot on the cable. In the high impedance mike
circuit a little capacitance will kill the highs.
73
Gary K4FMX
Brett Gazdzinski wrote:
The R390a is sold, Bob (wa3gfz) jumped on this one and picked it up
last night!
I have had that R390a for about 20 years, and its been working fine
for the last 15 years at least, after a rash of broken gear clamps
the first couple of years I had it.
I hope Bob has as good a performance from it as I did.
I don't know how things are normally done as far as selling,
but I think Bob actually called my house first, and left a message
with my son.
I still have the like new SX17, which I thought sounds better
than the R390a audio off the detector into the Marantz amp.
I now have an almost empty rack for the new project, I may move
the push pull 812a rig rack into its spot, if I can find a place
for the audio power amp, the only thing in the rack now.
Or, maybe I will leave the racks in place and move the 812A
rig into the empty rack, its closer to the operating desk.
The new rig (pair of 4D32) is coming along nicely so far,
the RF deck is drilled, punched, and painted, just needs to be
assembled, then its onto the RF control deck.
I am making the decks so they can be used with anything,
variac bias supply, variac screen supply, etc.
The RF deck is 40 meters only, but if I want, I could build an
80 meter deck to go with the 40 meter one.
The push pull parallel KT90 modulator deck is laid out parts wise,
and I have all the parts needed for it.
One power supply deck parts are gathered, I think I will do separate
variac supplies for RF and modulator decks.
I made an interesting discovery Sunday.
I have had a few reports of my audio not having a lot of highs,
even though I boost the mid and upper voice frequencies.
There is nothing to limit the highs in any of the rigs, other
than the mod iron, and even crappy mod iron will typically pass
high enough frequencies to sound good, and found the cord between
the mike preamp and the power amp was the problem.
It was a 15 foot piece of rg8m, the little coax, with phono
ends on it.
You would think something that works for RF service up into VHF
would be able to pass high audio frequencies, but no.
I wonder why it was so poor for audio, cutting stuff above
about 3000 cycles a lot????
Brett
N2DTS
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Brett Gazdzinski
Sent: Monday, January 12, 2004 11:13 AM
To: [email protected]
Subject: RE: [AMRadio] RE: r390a, sx17, t4xb for sale
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