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Messages - NJQA

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226
Equipment / Re: General Coverage Comms rxer down to 20KHz?
« on: January 06, 2020, 1313 UTC »
K1EL has abandoned efforts to revive the Palomar VLF converter.

https://www.hamcrafters2.com/VLFX.html

227
Longwave Loggings / DCF77
« on: January 04, 2020, 0426 UTC »
I was hearing DCF77 on 77.5 kHz tonight, well enough (in Midland, Virginia) that my KiwiSDR was able to decode the time.

228
Equipment / Re: What Radio Did you start your listening hobby with?
« on: January 01, 2020, 1553 UTC »
I started when I was in 5th grade with a Hallicrafters S-72 receiver that belonged to my Dad.  I enjoyed tuning around, but didn’t really know what I was doing.  The S-72 eventually died and I got a Hallicrafters S-120 for Christmas.  The S-120 was a bit better than the S-72, but not by much.  I had really wanted a receiver with an S-meter so I was a little disappointed.  Over the years I learned more about the hobby and got a few QSL cards.  Then one Christmas when I was in High School, I got a used Hallicrafters S-85.  The S-85 had an actual RF amplifier stage (the previous radios ran the antenna straight into the mixer).  OMG, what a difference.  I could hear so much more.  I added a Hallicrafters S-meter right between the dials (it looked just like a SX-99 then) and a Heathkit Q-multiplier.  Using an amplified loop antenna I built, I heard all sorts of AM BCB DX, including trans-atlantics. 

In one of Bill Orr’s (W6SAI) books he recommended not getting a top of the line receiver at first, but starting with an entry level set and learning to properly operate it.  Once you have squeezed out all the performance it is capable of, then upgrade.  I can see the wisdom of that, but doubt that anyone has the patience to do that these days.  Plus, today you get so much better performance with even the cheapest radios.  A $100 RSP1A is a zillion times better a receiver than that S-120 was.

I miss that S-85, but can’t stand to even look at a S-120.


229
SDR - Software Defined Radio / Re: New kiwiSDR Update
« on: January 01, 2020, 1128 UTC »
The DRM mode is disabled if the receiver is in the 20 kHz mode.

230
General Radio Discussion / Re: TDoA Questions & maybe an article?
« on: December 31, 2019, 1303 UTC »
The other factor I didn’t see mentioned is where some receivers are getting single hop reception and others are ground wave or multiple hops.  That will impact the position estimate unless the TDOA algorithm corrects for that.

The varying height of the reflecting ionosphere (which can be different for each receiver site) impacts the accuracy.  Picking receiver sites on either side of the day/night terminator could have an impact on accuracy. If you could get receiver stations that all heard the xmtr via ground wave then the position estimate could be very good...but you already have a good idea of where they are then don’t you?

Chris is right - modern day DF networks will spit out a lat/lon on a station in a fraction of a second. I imagine the biggest delay is just ensuring that all stations in the network are hearing the same station. All that is left at that point is to send a van through the area and find the specific house. If the FCC wants you, they can find you with little effort.

The biggest issue for pirates would be hobbyists doing their own DF work, getting a good location, publicizing their results, and drawing attention from the FCC. 

“The nail that sticks out is the one that gets hammered.”

231
Equipment / Re: Harmonics
« on: December 31, 2019, 1221 UTC »
If their fundamental frequency is 1160 and you are hearing them from 1010 to 1320, then “harmonics” is the wrong term.  Harmonics will be heard at integral multiples of the fundamental frequency (2320 kHz, 3480 kHz, etc).

It sounds more like InterModulation Products (IMP).  While it could be a problem at the station, it is more likely due to something in your receiver or your antenna system.  Is this the strongest station at your location?  Do you hear the same problem on different radios or using different antennas?  If you drive to a location further away, do you still hear the same problem?  Do you hear just that station, or do you hear other stations mixed together too?

232
Equipment / Consumer grade antenna splitters
« on: December 27, 2019, 1443 UTC »
KA7OEI has a good article on the use of consumer antenna splitters for ham/swl purposes.  I wasn’t aware of the problem with using “satellite only” splitters at lower frequencies.

http://ka7oei.blogspot.com/2019/12/using-tv-type-75-ohm-splitters-and-taps.html


233
This is fascinating to me.  This is a good transmitter fingerprinting tool.

Many years ago we would identify multiple carriers on a frequency by using Sub-Audible Heterodynes (SAH).  If two carriers were on the same frequency and differed by a small amount, your S-meter would show a small periodic oscillation up and down.  If it did this twice a minute, the two carriers differed by two hertz.  You had to factor out variations due to propagation and if there were multiple signals there it was hard to tell anything useful, but it worked somewhat.

You do exactly the same thing when calibrating your boat anchor frequency marker to WWV.   At some point you would no longer be able to hear an audible beat note and you would look at the S-meter for that point at which the small variations stopped.

Back in the seventies I would hear AM radio stations perform periodic frequency checks by broadcasting a tone and an independent lab some distance away would measure their transmit frequency.  It always amazed me that they could do this on graveyard channels where dozens of carriers were simultaneously present.  I don’t know how they did this, but I suspect that the audio tone they transmitted must have been accurate to less than a hertz.  The remote lab probably zero beat that tone on either the upper or lower sideband, measured the actually RF frequency of the tone, and by subtracting out the audio tone frequency would have the transmitted carrier frequency.  That’s my guess...if any of you station engineers can provide further insight I would be interested.  I don’t know how they accounted for frequency variations due to skywave effects.

234
SDR - Software Defined Radio / Re: New kiwiSDR Update
« on: December 26, 2019, 1247 UTC »
The narrow AM and narrow CW options are still there, though it took me a little while to find them.

Click on either the AM or CW button to select that mode.  Now click again on the same button to toggle between normal and narrow bandwidth.

235
General Radio Discussion / Re: Calibrated receive frequency
« on: December 21, 2019, 1548 UTC »
Once I went the SDR route, I gave up on using radio with knobs. Barbaric  :)

Knobs aren’t the issue.  Isn’t it really giving up on the use of radios without spectral displays?  Listening on a conventional radio feels like driving with blinders on.   I gotta know what is going on around me.

236
General Radio Discussion / Re: WQFG689 antenna
« on: December 20, 2019, 1258 UTC »
Is DX Toolbox for the iPad going to be updated for these features?

237
General Radio Discussion / FT8
« on: December 18, 2019, 1347 UTC »
A pet peeve of mine is when I hear someone claim FT8 operates with signals below the noise floor.  It works well, but there is no magic here.

https://tapr.org/pdf/DCC2018-KC5RUO-TheReal-FT8-JT65-JT9=SNR.pdf



238
The April 2016 issue of QST had an article by K1KP on his experiences with his solar panel installation, including what he did to control RFI.  There was some good advice in the article.

240
There is the nice Elad TMate 2.  It only costs three times the cost of a RSP1A.

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