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พนันบอลออนไลน์ pantip_จัดอันดับเกมสล็อตที่เล่นบนแท็บเล็ต_วิธี เล่น คา สิ โน สิงคโปร์_บาคาร่า ออนไลน์ มือถือ_คา สิ โน ออนไลน์ ถูก กฎหมาย

We are scrapping several old transmitters these last few weeks as part of a site upgrade? A couple of Harris FM20 and 10H transmitters are out the door.

Harris FM20H transmitter, circa 1970

Harris FM20H transmitter, circa 1970

Some people like these transmitters. I am not one of those. I found that they were of dubious reliability, tended to drift out of tune and have AM noise problems, and had multiple catastrophic failure modes. If it was not tuned just right, it also had a tendency to have HF oscillations and internal arcing in the PA cabinet.

Harris FM20H3 PA cabinet modification

Harris FM20H3 PA cabinet modification

This transmitter had a non-factory authorized modification installed as a tuning aid.? Tune for best efficiency, minimum AM noise then check and see if it is arcing.? It is also advisable to wear hearing protection during the tuning process.

Harris FM20H3, circa 1972

Harris FM20H3, circa 1972

This particular transmitter was my nemesis for a couple of years. It is actually possible to hate an innanimate object, I can tell? you. Goodbye you piece of shit.

We tend to scrap these instead of dumpster them.? It saves the client a little bit of money on dumpster charges.? If all the metal is sorted out by category, e.g. all the copper windings are cut from the HV transformer and PS filter inductors, all the brass, aluminum, and wiring harness are separated, then it is almost worth the time and effort.? Personally, I’d rather see all that material reused than land filled.

30 comments to Goodbye you piece of junk

  • Pedro

    Hello !
    I think many of the parts could be used as spares for some models still in use or for Ham radio constructions.
    Personally I also like very much the old stereo receiver on the last picture, did that went to the “recycle bin” too ?

  • Gregg

    Thirty-two years ago, my mentor introduced me to the fun side of broadcast engineering with a FM20H3. I spent several hours with a cold chisel carefully opening the PA door, which had spot-welded itself shut.

  • Paul Thurst

    Pedro, Unfortunately, these transmitters can not be parted out or donated, only disposed of. Those are the rules of the current station owners. The receiver you saw is still at the transmitter site was not a part of the disposal project.
    Gregg, I’ll bet that was a fun project.

  • Joel Epley

    Paul, might they be available for outright sale (for parts)? I’m in New England, and can pick them up myself. Thanks, Joel

  • Paul Thurst

    Sorry Joel, can’t do that either, in fact, the transmitter has already been scrapped. If I ever come across anything that can be donated or sold, I will post about it.

  • Gregg

    Yeah, it was fun. ?? Good learning experience…an early lesson on the importance of tight RF connections, even if it was just a cavity door. Also why broadcast engineers have to know a lot more than just soldering. I joke with an IT guy I know that he just has to know IT, while I not only have to know IT, but audio, RF, HVAC, woodworking, metalworking, electrical, plumbing…

  • Andy

    Still have an FM 20G and a 20H2 in daily operation. Kaboom!

  • Eric-KC7ES

    @ Paul: It was great day when we scrapped the decades old 20H3 on Phoenix and replaced it with a NV-10. Having said, that, it left the pad more or less functional. My local contract guy parted it out for “experiments in high voltage”. Needless to say, I was thrilled and didn’t ask questions. I do remember as a young buck, being near a FM20K when it went off like a shot. Too much circulating current as a result of poor neutralization or such.

  • Gregg

    Kaboom, indeed! At the same time as my FM20 experiences, I got to take care of two FM2.5’s (one an H3 from 1972, the other a K from 1978). When that 50-ohm (?) resistor in the plate voltage circuit would explode, I would be a nervous wreck for several minutes. I still plug my ears when pressing Plate On buttons because of these things.

  • Chris R

    Can you say Continental 817A?

  • Paul Thurst

    817A? Is that the combined 816R’s? I’ve never seen one of those in the field, although I’ve worked on several 816R’s… They can be a little quirky, especially when the SCRs get old and start to leak current before they are turned on. The tube type IPA’s are also a bit troublesome now that 4CX250B’s are not made as well as they used to be. Generally, I have found Continental equipment to be pretty solid, provided it is regularly maintained.

  • Had many FM-20-H3 and FM-20-K’s over the years and with the exception of the very badly abused and overheated WCGY-FM-20-H3 (the newer FM-20-K was fine)all were very stable and reliable transmitters. Even the WCGY FM-20-H3 with some time and effort (lots of cleaning and cavity parts replacement) came back to full power and reliability until we moved the station down to Peabody with two new Harris HT-30’s. I will say that compared to Continental’s the Harris physical design and implentation left a lot to be desired. The Harris 25 K series was a slight improvement but little things such as the intolerable jet blower noise and the crappy power supply cover screw arrangement (stripped after two or three removals) why did they not use the butterfly fasteners like the RCA’s. and most deficient power supplies in the industry

  • KJ4MDG

    The 817A was a single-tube 60-kilowatt FM rig (NOT combined 816s). There were only about a dozen of them that were sold, and as far as I know there aren’t any left in the wild…they all went back to Continental. I lived with one for a few years in the late 80s-mid 90s. They were not very well-behaved boxes, and tube life was abysmal.

  • Chris R

    Our 817A was replaced by a 816R. Night and day difference. Continental did support the thing until the bitter end. Looking at it in a positive way, I did learn a lot about transmitters! The Chief and I spent many Sunday nights wrenching on the thing. Then there was the three tube DTV transmitter, hated to see it go. I figured out how to keep it running and cut down greatly on the middle of the night calls. This stuff can be fun!

  • Two 817A duds I know of were WBLM and KABL-FM, those transmitters were very uncharacteristic of Continental, maybe more to do with the Eimac tube than the actual transmitter. If I had been it the buying position I’m pretty sure I would have gone with a proven design dual 27.5’s 30’s or 35’s and a combiner, not an unproven 60 KW behemoth with all the eggs in one basket.

  • WBLM still has a continental but I don’t know if it is the 816R or 817. It is a single cabinet, backup to their main Harris HT/HD 60 (Yes I have it incorrectly marked on my page as a HT/HD 50, I will fix that).

    I don’t recall ever seeing inside that transmitter room you have posted here. Is it a station in the Northeast/New York or one of the ones you maintained in Florida?

  • Paul Thurst

    Mike:

    Good eye, I don’t know how you keep all that straight, but the top one you likely have not seen. It is the former WHUD site before the Nautel was installed in 2008. The bottom picture is WYJB as it looked last week. That spot is now a large empty area waiting for a backup transmitter.

  • The WHUD site now with the four Nautel cabinets is slick. I found that site to be one of the more impressive sites i’ve seen in my travels.

  • Nick Straka

    I have a 20H3 as a backup at one place… last time I fired it up into the AUX antenna, it threw lightning out the top of the cabinet! I also had a 3H that got s-canned at another place. That fine specimen is also the reason I flinch and plug my ears when I turn on any tube transmitter. BANG! I HATE these transmitters too. I wouldn’t mind pushing the 20H3 off the Prudential Building (it’s near Boston) and watching it blow apart at the bottom.

    Thank goodness I have an FM-20B as a main at that site. Would love a second BE, junk the Gates and rotate between the two mains, but of course that costs money.

  • Matthew

    I am about to begin a restoration of a FM20H, This unit has a build date of November 1971 and was our original flagship transmitter. It was only removed from service in 2002 now it has to go back in service as a backup. Parts are very hard to find!

  • Yes, yes, yes…

    but were these earth-shattering kabooms?

    There was supposed to be an earth-shattering kaboom.

  • Paul Thurst

    Hey Mathew, when you are done with the FM20H, I have an old AMC Pacer rusting away in the woods behind my house, do you want a crack at that? More seriously, if I come upon any more Harris FM-H series transmitters, I’ll shoot you a line.