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Author Topic: Museum Station K3RTV  (Read 10961 times)
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WA3VJB
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« on: November 25, 2012, 08:28:39 AM »

Starting around 9:30am EST Sunday Nov. 25 please listen for K3RTV, the on-air radio club of the National Capital Radio & Television Museum.

Johnson Ranger and a Hammarlund HQ-140X, antenna is an inverted Vee up about 40 feet.

7285Kc and up.

Issuing First Day of Operation QSL cards for those interested.

http://ncrtv.org

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Pete, WA2CWA
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« Reply #1 on: November 25, 2012, 01:30:39 PM »

I heard you after you broke into the ongoing roundtable somewhere around 10AM. Good signal into NJ, but audio when you initially keyed up, and for a 1 minute or so, had some strange buzz or hum (or maybe a combination of both). Over time as you transmitted, the buzz/hum slowly disappeared into just barely perceptible.
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
WA3VJB
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« Reply #2 on: November 25, 2012, 03:14:25 PM »

Tnx for the report, Pete. You should have checked in !
Or maybe you heard Tom's comment that he tunes out when a Flex turns up. ; )

One of the other stations in there also mentioned the hum.  The only thing I could identify is mechanically-coupled hum from an autotransformer unit not far from the operating desk, one of those constant-voltage regulator cores.

I turned it off and people said the hum was gone, but it may already have resolved itself along the timeline you heard.

Basic Electro-Voice dynamic into a mic comp/EQ, into a stock Ranger.

I was only on for about an hour, but the rig proved out.


* K3RTV-1stDay'.jpg (110.18 KB, 3060x1280 - viewed 1064 times.)
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W4EWH
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« Reply #3 on: November 25, 2012, 04:16:00 PM »

Basic Electro-Voice dynamic into a mic comp/EQ, into a stock Ranger.

I suggest you try it without the EQ box: I've had problems with them before. If that cures the problem, check all the grounds and change the battery. HTH.

73,

Bill, W1AC
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Pete, WA2CWA
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« Reply #4 on: November 25, 2012, 05:52:41 PM »

Tnx for the report, Pete. You should have checked in !
Or maybe you heard Tom's comment that he tunes out when a Flex turns up. ; )

One of the other stations in there also mentioned the hum.  The only thing I could identify is mechanically-coupled hum from an autotransformer unit not far from the operating desk, one of those constant-voltage regulator cores.

I turned it off and people said the hum was gone, but it may already have resolved itself along the timeline you heard.

Basic Electro-Voice dynamic into a mic comp/EQ, into a stock Ranger.

I was only on for about an hour, but the rig proved out.

You sounded good but, of course, not like from the home station. The only antenna I have up at this time is the 75 meter inverted vee fed with coax. 40 meter antenna is still on the ground. Been trying to repair/refurbish the tri-bander to get that thing back up. Outside temps in the upper 30's and low 40's doesn't make that easy.
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
WA3VJB
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« Reply #5 on: November 25, 2012, 08:44:04 PM »

Bill -- I don't think it was the external box this time, but yes, they are vulnerable to RF and ground loops. More testing needed. Mystery, intermittent hum is not my friend, especially since I'm not the only operator of the station over there.

Pete -- the external mic box dressed up the stock audio just enough, without asking too much of an unmodified amateur transmitter. There's a wide range of voices gonna be on that rig, so I may make the EQ settings even more generic than what you heard.

Most of the "demonstration" emphasis is on the receive end since the audience of museum visitors will be right there in the room.  The transmit part of the equation can be shortchanged a little to help guarantee a good operating experience among the volunteer staff with licenses.  Only a few have ever run tube-type transmitters, and as mentioned on here earlier, it's a challenge to cook up a standardized set of tuneup procedures.

Like how and why to zero-beat ?!?!?  That's one I got the other week.

Here's a snippet of some video I'm putting together from today. I can hear the autotransformer hum getting into the camera mic, so it's easy to figure the transmitter mic caught some of it too.

http://youtu.be/3x51W8gP754
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WA3VJB
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« Reply #6 on: December 01, 2012, 01:30:40 PM »


Doing a test this evening, 7PM EST Saturday around 7285Kc.

One of the museum volunteers is hosting a group of Tiger Scouts in a couple weeks and hopes we can demonstrate the station one evening. I'm a bit skeptical because of prevailing interference from international BC stations, but the test run will show what's what.
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