Messages

751

The RF Workbench / Re: A 500 watt Class E amp

« on: January 14, 2018, 0026 UTC »

I've seen his stuff before.  There is too much circuit strays to work on 40 meters, and one reason all his stuff is built for 80 meters.  The output transformer alone is 4-6 times the size it needs to be.  Also with class E, you usually need an adjustable output network to get the waveforms to where they need to be.

Again, 8 fets to get 400W?  really?

+-RH

752

Propagation / Re: is it me?

« on: January 09, 2018, 0725 UTC »

Don't worry as soon as I go on the air the band is guaranteed to go long within 10 Min

I'm glad it's not just me!

+-RH

753

The RF Workbench / Re: Any DDS 200 watt AM Transmitters or kits

« on: January 07, 2018, 1547 UTC »

Nearfield RFI can cause all sort of problems in the lab, which is the main reason I only use transformer based couplers to sample the RF.  Open air sampling is unreliable because the RF induces itself into the power line and reradiates mixing products of the carrier frequency and harmonics of 60 hz.  My house is so old the electrical system has no ground anyway, so I need to be careful working on anything as the signal ground is usually not at the same potential.

You can make a transformer sampler by winding 20-40 turns on a torroid of convenient size such as a T106-2 and passing the center conductor of your coax through it.  The winding should then be terminated by a known resistance, I use 10 ohm, 15 watt film resistors here.  It can all be built into a small diecast aluminum box with two N connectors for the RF and a BNC for the sample.

20 turns should yield around 24dBm @ 100W, 40 turns around 18dBm, still too hot to feed directly into an SDR, but fine for most real spectrum analyzers.

+-RH

754

The RF Workbench / Re: Any DDS 200 watt AM Transmitters or kits

« on: January 07, 2018, 0512 UTC »

If your not monitoring directly from an RF sample and attenuator from the output of the transmitter (i.e. relying on your receive antenna to pick up some signal leakage) you will get excessive hum and noise.  Check the output with a scope.  If its clean, your monitoring system is suspect.

+-RH

755

General Radio Discussion / Re: Looping mp3

« on: January 06, 2018, 1932 UTC »

Most of them should have a repeat 1 function.  Maybe repeat all with only one file?

+-RH

756

North American Shortwave Pirate / Re: Unidentified Radio 6940 USB 2230 UTC 5 January 2018

« on: January 06, 2018, 0114 UTC »

6940 KHZ USB 1-6-2018

Heard something right at threshold @ 0110Z that sounds like Bran Van 3000  'Drinking in L.A.'
0115z AC/DC of some flavor.
0119z Drastic change in signal strength, now S9+ with Korn 'Here To Stay'
0123z 'Unidentified Radio' ID

+-RH

757

North American Shortwave Pirate / Re: WDDR 4015 Was 6950 USB 0149 UTC 1 Jan 2017

« on: January 01, 2018, 0308 UTC »

Sounding good here on 4015 USB, about S9 out of AC/DC's 'TNT'.  Op talking about his layer dip...with guak...yuck! 0308z.
0310z Red Hot Chili Peppers 'Under The Bridge'
0320z Thanks for the shout! Variable between S8 and S9+10.  Nice choice on the unusual frequency.
0358z 'Come on do the fungai hut, its fungai lickin' good'...lol
0400z 'We Can Get Together' Icehouse
0610z still here with Fleetwood Mac 'Future Games'...striking resemblance to CSNY me thinks.
0707z still here with 'Aint No Sunshine'  Love this track.

How about some A Perfect Circle?  Thanks for the Smashing Pumpkins tune!

723z still going strong, I'm off to bed though.  Thanks Again!!

+-RH

758

General Radio Discussion / Re: Anyone have a spare 50Kw SW Transmitter ??

« on: December 30, 2017, 1855 UTC »

Nope, they had the PDM MW-50 modified to an SW-50.  There is apparently a problem with the fiberglass chimneys for the tubes.  As they age, they become more prone to carbon tracking and breakdown, which is what happened.

Funny, Allan says he wants to go back to a conventional push-pull high level modulated transmitter....I would advise against this, as his power bill might double.

Also He did mention there was no insurance.  Most of the radio stations I've worked for had some form of business insurance.  I can't imagine running one without.  In this business, you have a lot of exposure, towers that fall, buildings that burn, stuff that is pretty expensive to replace.

Just a thought,

+-RH

759

The RF Workbench / Re: Desoldering trick using a halogen lamp

« on: December 30, 2017, 0225 UTC »

The video suggests that this is for use in situations where a hot air iron isn't available.  I'd stand a better chance of having the proper tool than a spare halogen bulb and lab supply.

Neat Idea, although I worry about heat stress to the components being installed using this method.

+-RH

760

The RF Workbench / Re: Power Supply for TX

« on: December 26, 2017, 0547 UTC »

I've been using the LRS series supplies from mean well.  They seem to work well enough, a 24V supply should turn down to 20V or so.  Be sure to get one at least 2x your carrier power, 3X is better.

RFI can sometimes cause problems with switchers.  Brute force filtration may be needed in some applications.

+-RH

761

QSLs Received / Re: Radio Illuminati Christmas show eQSL

« on: December 19, 2017, 0146 UTC »

2KW PEP eh?  Sounds like someone got a new toy

+-RH

762

North American Shortwave Pirate / Re: UnId 6930 USB 0125 12/17/17

« on: December 18, 2017, 0127 UTC »

0123z 6929.985 KHz USB on with Tom Petty's 'Ready to Fly'
0125z OM talking about left coast, something about less than broadcast quality.  Rolling fades, about S8 on peaks.
0127z Tom Petty 'Refugee'
0130z OM talking about the FCC and Free Radio.  Into Tom Petty's 'Swingin'.
0133z OM talking about the FCC and the internet...'Gonna play some classic rock, some Doors...' Into Tom Petty 'You Wreck Me'

Thanks for the Show!

+-RH

763

General Radio Discussion / Re: Anyone have a spare 50Kw SW Transmitter ??

« on: December 17, 2017, 0017 UTC »

According to the audio, this was their main for 7490, backed up by another transmitter that for whatever reason only makes 30 KW.  My guess never having seen the place is that most of their transmitters are either missing parts for other frequency ranges, or have instabilities and are happiest on certain ranges.  Some of the pictures I've seen include old AEL/REL transmitters from military service in the 50's and as such parts are probably no  longer available.

You make due with what you have.  5% power beats 0%.....been there

BTW, RCA BTF-20E's had a similar problem where an arc would catch the tube deck on fire (which was made out of lexan).  The plenum blower would then blow flaming bits of plastic all over the room.  Quite a few failed in this way, and for that reason, RCA transmitters were banned from one of the transmitter sites in NYC.  I was happy to retire one in 2006 that had its fair share of close calls, and an ice storm the winter prior sealed its fate after running at 7% power for a week.

+-RH

764

General Radio Discussion / Re: Anyone have a spare 50Kw SW Transmitter ??

« on: December 16, 2017, 2350 UTC »

Hey redhat, check out this story of a a bit of a flame-fest from a MW-5's point of view:

   http://www.comcents.com/rg/mw5.html

Yup that one has been around the block a few times.  I don't think you can get the PWM choke anymore.  What a lot of engineers missed when repairing these boxes is a check of the damper diodes.  You needed a special test setup to test them.  If the damper diode stack was bad, your new coil and mod tube would fail in short order.

+-RH

765

FM Free Radio / Re: What are the chances of getting caught on FM with one watt?

« on: December 16, 2017, 0736 UTC »

             It really depends upon where you are, and whom the receiving audience is. If you are wayyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy out in the boonies, you maybe on for years without notice. However, in a metro area, or even a small town with a station manager, engineer, or a so-called concerned citizen, who is a real douche, chances would be pretty good since the FCC will respond to complaints. And? 1W not reaching anywhere? Really??? In the right location and elevation, 25mW and a well tuned quarter wave ground plane can cover a whole town. Push a watt behind that, and you can cover for miles. This all depends on antenna efficiency, elevation, and geography.  The other thing is, are you choosing a FREQ that is really empty? That's hard to do in many areas. Another thing is which FCC office has a bad reputation. In Alaska, the FCC has a reputation of being really tough up there, even thought most of that state is wide open. Since there's so much air radio depending traffic up there, the Anchorage FCC office wants the aviation band as interference free as possible. So, lots of variables. I'll tell ya what, this so-called AM Revitalization Program of letting every AM station litter the FM band with their own FM translators certainly has not helped things for either free radio, and especially licensed LPFM.

+1

+-RH