Search found 37 matches

by vk3alb
Wed Sep 18, 2019 9:54 pm
Forum: Spectrum Analysis
Topic: Setting up SDRuno to detect Amateur VHF tone coded squelch frequency?
Replies: 3
Views: 2705

Re: Setting up SDRuno to detect Amateur VHF tone coded squelch frequency?

Hi, Here's what I did. Tuned for a signal from a transmitter and looked at the audio spectrum. I zoomed in on the audio spectrum as much as I could to get the best chance of catching the PL tone. Note that I engaged the FMAP button. When I keyed up, the tone was really obvious. Since we know PL tone...
by vk3alb
Sun May 26, 2019 9:56 pm
Forum: SDR Antennas
Topic: Busy night of 40 meters
Replies: 4
Views: 3727

Re: Busy night of 40 meters

I think the point the OP was trying to make is the amount of CW in such a small span. That's what the WPX does for a band.
by vk3alb
Tue May 14, 2019 11:05 am
Forum: SDRplay related
Topic: MFJ 1708SDR question
Replies: 4
Views: 2557

Re: MFJ 1708SDR question

Hi NewYork, OK so 50dB isolation is probably about right for a single relay although I'm a little surprised it's not higher as the SDR input is grounded. I wonder what input you were using? The Hi-Z input picks up a lot of radiated signal. One option you have is to add some attenuation into the SDR ...
by vk3alb
Sat May 11, 2019 10:30 pm
Forum: SDRplay related
Topic: MFJ 1708SDR question
Replies: 4
Views: 2557

Re: MFJ 1708SDR question

Hi NewYork, I don't have this switch and looking at the manuals (incl the B variant) I don't see any isolation specifications but I can offer some suggestions. Easiest thing, ask MFJ what the isolation is for your unit. They should know but if you don't get a satisfactory answer you can do you own t...
by vk3alb
Fri Feb 08, 2019 8:11 pm
Forum: SDR Antennas
Topic: Extending the range of a Discone antenna down to 3.6 MHz
Replies: 52
Views: 22089

Re: Extending the range of a Discone antenna down to 3.6 MHz

Thank you both. An excellent experiment.
by vk3alb
Fri Feb 08, 2019 12:45 pm
Forum: SDR Antennas
Topic: Extending the range of a Discone antenna down to 3.6 MHz
Replies: 52
Views: 22089

Re: Extending the range of a Discone antenna down to 3.6 MHz

Hi Glovisol, Yes it seemed to me that the electrical earth may be acting as an antenna for things other than interesting radio signals. I have seen noise carried by mains wiring cause significant noise on HF. Normal noise reduction techniques using ferrite cores applied to the wiring brought a great...
by vk3alb
Thu Feb 07, 2019 7:54 pm
Forum: SDR Antennas
Topic: Extending the range of a Discone antenna down to 3.6 MHz
Replies: 52
Views: 22089

Re: Extending the range of a Discone antenna down to 3.6 MHz

Here is the detailed report: 1) The antenna is mounted on a 1.8 m steel pole which goest through the roof and is mounted with two steel brackets to a wooden beam of the roof. There is an elecrical (not RF!)) ground tied to the pole which was wired ages ago and is connected to the general electrical...
by vk3alb
Mon Jan 21, 2019 8:55 pm
Forum: General
Topic: Your MFJ-1708B-T/R Switch Experiences
Replies: 4
Views: 3241

Re: Your MFJ-1708B-T/R Switch Experiences

Ruben_NB4R wrote: I don't know why the SDRPlay don't make this standard practice if it is so needed.
Ruben_NB4R
The RSP2pro comes in a metal box but also comes at a price. As has already been mentioned not everyone needs such heavy shielding.
by vk3alb
Wed Nov 14, 2018 8:22 pm
Forum: SDRplay related
Topic: Bias-t voltage
Replies: 5
Views: 3596

Re: Bias-t voltage

I think the reason for the 5V bias voltage is understandable.

As someone mentioned there are lower voltage circuits of the mini-whip https://www.g8jnj.net/activeantennas.htm
by vk3alb
Sun Nov 11, 2018 12:22 pm
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 30
Views: 18674

Re: A FOOLPROOF ANTENNA SWITCH

Hi All, Thanks for the comments and suggestions. It shows that even in a simple circuit there may be room for improvement. Here then is the revised circuit with bypass caps and back EMF diode across the relay coil. I was lazy this morning and left them out. Not surprised that I was caught. :) RX iso...