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 on: Yesterday at 03:47:40 PM 
Started by N1IC - Last post by YU3MA
This kind of designs really deserves much much better A/D converter than RTL2832U ("famous" IC in DVBT SDR dongles) especially if you spend so much time in all other segments, connectivity, DSP, software etc.

If we look like this, one Raspberry Pi + low-cost DVBT dongle can have almost similar features for much lower price, so take one step above that and use some "serious" A/D converter, for example 12bit 80-100MSPS!
Also, for HF guys make it switchable to work as direct-sampling receiver (skip tuner) and that will be much interesting for most people, including me Smiley

 on: Yesterday at 03:47:06 PM 
Started by KC1CJN - Last post by KC1CJN
1. Random/Long Wire:  I have not yet gotten that FC-40 to match a wire - I always get HSWR on the FT-897D. Tomorrow, I'll take the cover off and look at it while someone hits the tune button on various bands. Might be it just doesn't work!

2. 64ft Aluminum Mast:  I can, of course, telescope the mast to a desired length, so can pick my preferred bands, as I understand. Would there be a better use of the mast maybe? Should I put up and inverted "V" dipole or "L" or other antenna using it as support rather than using it as an antenna?

 on: Yesterday at 03:45:07 PM 
Started by SHORTWIRE - Last post by AC5UP

Many moon ago I did a newsletter piece on creative vanity and standard issue calls.  You'll find a plethora of them starting with the N0 prefix:

Meanwhile, on the broadcast side, there was this............

 on: Yesterday at 03:39:52 PM 
Started by WA7IRY - Last post by WB6BYU
Quote from: W5WSS

K4SAV Hello can you expound on why a 23 ft vertical is performing as you stated "too high an angle for 10m,12m."and What modeling software did you use?

23ft on 10m  should be a pretty good length to provide a good utility for low angle pattern there.

Any working modeling program will show this.

5/8 wave on 10m is about 20' (hence all the CB antennas of this dimension.)  Anything long than
that will result in less radiation at low angles on 10m.  It doesn't drop off that sharply, however,
as long as you look at the actual radiation at a specific angle rather than simply the angle
where radiation is maximum (because there are multiple lobes in the pattern.)

Because the radiation from the bottom of the vertical is often broken up by nearby buildings, etc.,
using 3/4 wavelength isn't that much worse than 5/8, and even the standard 43' vertical is only
1dB or 2 dB down on 10m and 15m from the optimum 5/8 wavelength levels.  So longer antennas
tend to still be usable.  Shortening it too much reduces efficiency on the lower bands, however,
and I wouldn't want to go any shorter than perhaps 24' if effectiveness on 40m is important (unless
you provide some sort of loading in the center or top of the antenna.)

So increasing the height of the vertical will improve 40m performance somewhat, while shortening it
may improve 10 slightly.

 on: Yesterday at 03:38:34 PM 
Started by KW4CQ - Last post by VK3AMA
I'm running W7 pro 64 bit and JT65-HF Version Radio is Yaesu FT-897d. The JT65 installation located the log here: C:\Users\Dennis\AppData\Local\JT65-HF\. The log file name is: JT65hf-log.csv. Both location and log name were accepted as defaults during the JT65-HF installation. The file (JT65hf-log.csv) is automatically updated whenever I transmit or receive a JT65-HF signal. This happens automatically ..... no need to click JT65's "Log QSO' button. I never figured out how to disable this automatic update.

Not correct. The JT65hf-log.csv is a decodes, RX & TX, history file, NOT the log file. The log file is an ADIF file and the location is shown in the JT65-HF "Log Contact" window which appears when the "Log QSO" button is clicked. The location of the Log file can be altered while the "Log Contact" is visible.

de Laurie, VK3AMA

 on: Yesterday at 03:37:19 PM 
Started by W4CP - Last post by AA4HA
Regarding antenna separation;

a 50 watt radio is putting out about 47 dB of power to the antenna.

Five feet away you have another antenna attached to a receiver that is really happy with signals from around -40 to -110 dBm.

Parallel vertical antennas. The coupling between the two is pretty effective at a few feet.

Receivers generally do not like seeing high RF fields being directed into the FET front end.

At five feet what do you think the field strength is?

Sure, there are stages in the receiver that makes the receiver more selective to its frequency but the first RF stage (or pre-amp) usually does not get a selective frequency. It sees (and tries to amplify) everything coming in the front door.

Generally we tried to keep the front end of receivers from seeing more than -40 dBm. Usually above that point we would get excessive AGC action and distortion. One of the other things that gets cooked are PIN diodes.

 on: Yesterday at 03:31:42 PM 
Started by AD5VS - Last post by AD5VS
Thanks for both replies. Looks like I could easily damage something in the tuner if I leave it in line during high power transmitting. I'll continue to take the 993b out of the RF path when transmitting greater than 300 watts either with a transfer switch or by reconfiguring coax cable connections.

 on: Yesterday at 03:30:00 PM 
Started by K6JHU - Last post by WB6BYU
Quote from: K6JHU

Not sure what the EOC has for a radial system. I suspect they are using a GR5V (no radials required).

That will be horizontally polarized most likely, so it won't work well for ground wave coverage.

It is possible to adapt it for vertical polarization as a "T" antenna by shorting the twinlead at the
base and feeding it against ground (which does require radials.)  But since all the other stations
they expect to work will be using NVIS, this might not be practical operationally.


 My vertical system uses 26 radials of 33' each. Definitely what I believe is a decent radial system :-)

How high is the vertical antenna you are using?  How is it loaded on the lower bands? The
question is not just the radial system but the overall antenna efficiency.  For 80m and
especially 160m you're going to need a pretty tall vertical to manage good efficiency, and
you still have to deal with the low conductivity soil along the desired path.  (Radials won't
help that, unless you can run them for 26 miles...)

A horizontal dipole at 20' will provide much better signals under most conditions.

 on: Yesterday at 03:28:07 PM 
Started by W4CP - Last post by AA4HA
You do not need to do a mod to RX on CB frequencies. Just like you do not need to do a mod to listen to shortwave broadcasts.

 on: Yesterday at 03:22:19 PM 
Started by K1UO - Last post by WX7G
Stainless steel appliances are out of style and white is in.

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