Search found 29 matches

by vk3alb
Wed Nov 14, 2018 8:22 pm
Forum: SDRplay related
Topic: Bias-t voltage
Replies: 5
Views: 1185

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: 10
Views: 2510

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...
by vk3alb
Sun Nov 11, 2018 3:50 am
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 10
Views: 2510

Re: A FOOLPROOF ANTENNA SWITCH

Hi Roger,

Yes I see that now. In that case, as long as the PTT (SEND) line can sink at least 10mA it can connect directly to the base of Q2. Then, remove D1, R2, R3 and Q1.

Thanks for the feedback.
by vk3alb
Sat Nov 10, 2018 11:04 pm
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 10
Views: 2510

Re: A FOOLPROOF ANTENNA SWITCH

Thank you to Glovisol for his excellent and elegant circuit. As he says in his text there is a way to protect the receiver in case of failure of the 12 volt supply to the circuit. I think my version of his circuit was his intention. RX Isolator.png Consider the modifications of his circuit as shown ...
by vk3alb
Sat Oct 13, 2018 9:23 pm
Forum: SDRplay related
Topic: RSP1A - RF Damaged?
Replies: 5
Views: 1642

Re: RSP1A - RF Damaged?

Hi John,

How do you know it is damaged?
What tests have you carried out?
Most things are repairable - for a price.
If it really is damaged your first stop is to seek advice from SDRplay support
by vk3alb
Sun May 20, 2018 8:54 am
Forum: SDRplay related
Topic: HOW ABOUT A TRACKING GENERATOR?
Replies: 3
Views: 1322

Re: HOW ABOUT A TRACKING GENERATOR?

One of our group is working on a spectrum analyzer package for the SDRplay. He talks about the challenges of including a tracking generator.

viewtopic.php?f=12&t=3164
by vk3alb
Wed Apr 11, 2018 6:43 am
Forum: General
Topic: Creating a 12 volt bias T for any RSP model
Replies: 2
Views: 1339

Re: Creating a 12 volt bias T for any RSP model

I don't understand your concept of reverse in this description. It sounds like you are simply planning to use the bias tee the correct way. The tee has a DC supply input. This DC is fed to the coax/socket that goes to the preamp/antenna system. The remaining coax/socket has a DC block (capacitor) an...
by vk3alb
Wed Jan 31, 2018 7:27 pm
Forum: General
Topic: Enough protection with antenna switch?
Replies: 10
Views: 3921

Re: Enough protection with antenna switch?

I think it's important that every user take heed of what radioham has found. Doing a measurement like this put him in control of protecting his own gear and gives him some understanding of his own systems performance. One thing he could do is add a second changeover relay in the RX leg that switches...
by vk3alb
Sun Dec 24, 2017 11:24 pm
Forum: General
Topic: RSP2 RF Protection Question
Replies: 11
Views: 6160

Re: RSP2 RF Protection Question

Thanks Support, It strikes me that 75W is quite a bit of power for satellite work but I don't know Jim's situation. I suggested low power TX because that will offer Jim nearly 19dB of extra protection during testing. Assuming no losses in the system(s) 1W = 30dBm add 50dB attenuation = -20dBm = a sa...
by vk3alb
Sun Dec 24, 2017 9:38 pm
Forum: General
Topic: RSP2 RF Protection Question
Replies: 11
Views: 6160

Re: RSP2 RF Protection Question

Hi Jim, I think you first need to assure yourself that your scenario won't blow out your RSP. In this situation +10dBm is a HUGE signal and if S9 = -93dBm then according to support S9 + 103dB is the absolute maximum signal level you should ever measure at the input to the RSP. If you don't have meas...

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