• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

the ATU in front of a series fed AM antenna

Indeed another fine product of the Q-T-W, they sure made a lot of them. Good for the time when the match to the transmitter was not a critical as it is now and "Q" no big deal. There was a lot of latitude and forgiveness in those BC-250GY's, BC-1F, G, H, on-and-on! In any configuration, "T" or "L" tough to adjust. Best config as "L" using part of the inductor to trim the shunt "C" and the rest as line or antenna side element depending on if the antenna Z is higher or lower than the line Z. Congratulations on getting it tuned, some times it gets down to 1/8" coil clip increments at a time mutual coupling and high Q made final adjustment tedious!

Best regards,
w/
 
(Going back to suprises in the ATU)
When Birach communcations had bought WNWI 1080 but not yet moved it to Oak Lawn IL,
it had gone silent a while. Then it reappeared, with a signal about half of what it had before..

On a visit to NW Indiana, I had to stop in and see what was up...
No one inside the station.....walked out to the tower and in the ATU hut, found a college student
with a computer and a little xmttr, doing the very minimum necessary to keep the license valid.

The hut was about the size of a little chicken coop, and I don't know if I'd want to sit at the bottom of the tower
unless I could bring my own radio to hook up at the end of the day.

I've heard stories about the signals they got when they hooked up the WWV receiver to the stick some nights. :)
 
Yes. My experience with the one I recently tuned was the same. LOTS of trial and error with the OIB. I've got it pretty close but at some point I'm going to revisit the site witha few extra toys and super-tweek it. The day I tuned it up it was freezing cold with the wind blowing, etc. Needless to say I can take more time on the next visit to get it 100 percent perfect. I'm real close though. After I get it perfect I'm going to mark the heck out of the coil with a magic marker on the exact correct spot, etc.

Before I started it was 30 ohms 0J into the input of the ATU. Now it's 50 ohms with 1 ohm of reactive. I'll try to get that down to 0. :)

I recently purchased a AEA HF SWR Analyst unit. I've tried it on a couple other AMs just to see how it works. This station is above 1000 and a long ways from other AMs so it should give me a pretty good visual of my bandwidth moreso than a generator and the OIB, etc.
 
Watt, I've owned both a 500GY and a BC1-F. They are now "rusting in peace." Both sites had the Gates single coil tuning unit (I'm sure them Quincy guy's gave it a snazzy name, like the "Hi-Watter Miracle Tune.") Anyway, both rigs were replaced with ND-1's. The site with a series fed tower worked ok. The other site was shunt fed, using the sloping wire method. It would tune up, but the match changed with the weather. When I heard the station doing VSWR trips on modulation peaks, I knew it was time to head to the site to readjust. Fortunately, I re-licensed that station to another city, diplexed into another tower and got rid of the darn ATU. Now, I have this huge coil in the shop that I salvaged. Maybe someday a 540 will need it.
 
One big coil in a DA? Maybe not in the ATU but were in some phasors. One big coil tapped for each tower!
One still exists around here. It's got a real narrow bandwidth.
Each tower also have individual phase & radio adjustments.
 
boiseengineer said:
One big coil in a DA? Maybe not in the ATU but were in some phasors. One big coil tapped for each tower!
One still exists around here. It's got a real narrow bandwidth.
Each tower also have individual phase & radio adjustments.
Click to expand...

Not an uncommon practice back in *THE* day! Long ago I worked at a 4-tower DA-2 (2-day, 4-night) that used large resonated inductor with the feeds to the xmission lines coming off the taps. Phasor was the RCA concentric transmission line (62 ohms IIRC) and ltu's at the towers. Spacing between 1 and 4 was .764 mile.

Now as far as use in a ltu goes, up until 2003, all WSM used for atu was a large inductor parallel resonated with a 2000 pf Lapp gas filled cap. The 230 ohm line tap was about 5 turns tower on the coil than the tap going to the tower. Parallel resonant ckt = good auto-transformer and reactance eater, but bandwidth not to good.

"Tanks" for the memories! ;D

w/
 
The resonated coil tapped to each transmission sounds like a distributive phasor (I'm probably getting the name wrong, but "A. Earl Cullen" comes to mind).

There were also the "jeep coil" phasors where one big multi-tapped coil fed each of the phase shift networks. I've had good luck converting some of those to a parallel power divider scheme.

Guess I'm wandering off topic. Sorry.
 
stacker said:
The resonated coil tapped to each transmission sounds like a distributive phasor (I'm probably getting the name wrong, but "A. Earl Cullen" comes to mind).

There were also the "jeep coil" phasors where one big multi-tapped coil fed each of the phase shift networks. I've had good luck converting some of those to a parallel power divider scheme.

Guess I'm wandering off topic. Sorry.
Click to expand...

Thats right on the type of DA system and yes, A. Earl Cullum built a lot of these. I saw personally more than one with his design and consultancy. Long story there!

Best regards,
w/
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom