I've been reading the mail here, and saw my call so had to reply. Hi
Jim. Yes that was a great road trip to pick up that 314R1 BC
transmitter. Correction: I did it with 1985 Cheby S10, with 3 L V6.
It went fine except for the radiator hose which blew N of Denver.
Lucky I had all tools with me for the transmitter, so that I replaced
it at the parking lot of the Loveland NAPA parts store.
I went over LaVeta Pass (9413 feet ASL), E of Wolf Creek Pass. Waited
until early in the morning when it was cool - for the engine. Then
South at Ft Garland, CO, to Taos and home. As soon as I got home,
grabbed the neighbor and spouse to help unload the TX - spent all
Sunday cleaning it in the carport as the owner up at 1230 Kc was a
smoker. The biggest mess was in the scroll of the blower, where
there was a sort of gunk coating. Took it all apart and made it lke
new.
I was looking at the transmitter this morning while I listened to 75
meter AM activity, several guys on 3875, 3885. Its been really nice
this winter, the clarity. Although I have a 75A3 with a bum 6 KHz
filter, I am using an JRC NRD-535 Rice receiver which I bought from
a fellow in Arkansas. It is extremely user friendly and has 6 and 12
KHz bandwidth filters, so AM comes through really hifi is there are
no slopbuckets spilling over nearby.
I gotta repair the TX again, I blew up the PDM driver transistors
when I was testing them into a 110 ohm load (which the tech at
Continental recommended). Its kind of nice restoring a BC rig which
still has customer support available from the factory. They sent me
an updated manual/schematic for it. The only hitch has been
increasing THD which appears in the audio at higher modulation
levels. It can be seen on spectrum analyzer as 20 KHz spurs both
sides of carrier, and it also shows up on the demodulated audio on my
AM90 mod monitor as a parasitic in the audio. Being a switching
modulator, it isn't so easy to troubleshoot as a class B high level
plate modulator. I had upgraded the driver card which takes fiber
optic input from the PDM generator and drives the 3-500Z switch tube.
Modified it per Continental schematics to use MOSFETS instead of the
multitude of old HV bipolar NPNs. So something is wrong in there. But
then I popped the silicon testing it into the load. I hope that, when
done, it will be a reliable transmitter for the frequency conversion.
It uses a 2 x fout crystal, so will need 3 - 8 MHz source for 160 or
75 neter output.
Spent some time building a 1 kW dummy load, to test it to full
output. That was a moderate success as the two 12 inch Globar-like
resistors I settled on had horrible tempcos, and VSWR would drift up
as they got hot (107 deg C on the surface, had a high velocity fan
blown on them). I have been wondering where I could find one of those
toaster element (Ohmweve resistors) built-in dummy loads like Gates
used to build into their BC rigs. Anyone got an extra one for cheap?
A ham acquantence in Illinois also bought a PowerRock 314R1, serial
number 1, which is in Idaho I think he said. He has been working up
ideas for changing the PDM filter to begin rolloff below 10 KHz, say
at 6. This would relax the spurious output specs of the multi-node
bandpass RF output network by tightening the modulator low pass
filter. Another improvement Greg has recommended is to use a step
down on the primary of the HV transformer to drop the HV, keeping the
correct load impedance on the 3-500Z finals at legal ham limits. Also
it would keep the PDM duty factor high at reduced output for lower
distortion. With 8500 volts negative in that thing, its a little more
scary than a Gates box.
I have since acquired a 2003 Tacoma with a real hitch (not one of
those bumper ball mounts) and a little trailer, for future
acquisitions. It is much stronger than the S10 was, (and
airconditioned). And it has a big fuel tank, really important in the
open country of the west. In New Mexico, I don't think twice about a
weekend run down to Carlsbad or to Alamagordo (its about 300 miles to
Carlsbad) for my other hobby. Its so straight and open, not like
driving up I95 from Baltimore to Philly with 4 lanes of traffic wide.
I was astounded with WY though, really a wide open state there! I
suppose you have real winter right now. It was 11 deg this morning
here, no snow now, but 2 days ago....
I'll get the rig on the air someday, meanwhile will keep listening
and enjoy the holidays with the YL .
Happy Holidays and may your finals glow orange.
73
John
K5PRO
Jim Sez:
Todd:
Yours is the second transmitter to make that pass. John K5PRO came up to
Casper last year to pick up a Continental 1KW from Los Alamos, NM and went
back that way to avoid some traffic. He pulled a trailer with a 4 cylinder
Ford Ranger hauling the 850 lbs plus trailer.
People in the 70s wondered why the western states were so against the 55 mph
speed limit. Drives out here are measured in hours and the times your
brother mentioned are probably at 80 mph or more. The nearest town that we
drive through going south is Wheatland and that is 1 1/2 hours from Casper,
Cheyenne (next town to go through) is 2 1/2 hours. Cheyenne exit is #7 and
my Casper exit is 185, long trip at best. We don't have roadside call boxes
either.
73 Jim
de W5JO
Last July I drove from northern New England to the southwest
corner of Colorado to pick up a broadcast transmitter. 2400+ miles each
way, we did it in 5 1/2 days. Took my dad along too, he had a blast. Our
only detour was to visit the Four Corners monument before coming back.
Made me wonder how many others out there had hauled a 1400 lb
> transmitter up through Wolf Creek Pass?
Then Todd Sez:
So I'm not crazy at all, then. Good to know! We made the trip with a
Ranger also, 4.0L V6 though. Picked up a U-Haul trailer out there and
loaded it, brought it back. This one is a Collins 300G, so it's only 250
watts, which really skews the power-to-weight ratio.
