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Has anyone ever tried using the CW output feature to generate a carrier for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only receive AM mode signals? It seems like this should be thoretically possible by attaching a small whip to the nanoVNA and placing it in the vicinity of the receiver. But probably tricky to get the exact frequency dialed in, as well as the signal strength relative to the sideband signals. Just seems like a fun radio exercise or for an emergency need.

Hi Bruce,

Yes, I have done something similar using my NanoVNA SAA-2N. I set the NanaVNA to a particular CW frequency, but have only used it to test effects of using a filter or amplifier at the input of an SDR dongle. I haven't tried using it to inject a simulated BFO signal into an AM-only capable receiver to receive SSB. I'm not sure how finely one can adjust the frequency on the NanoVNA, but what you describe should be possible. You could use various lengths of wire attached to the CH0/S11 center conductor to adjust the level of coupling to achieve higher or lower levels of "injection"of the BFO signal.

I remember years ago tuning an AM-only shortwave receiver to a SSB signal of interest, and using another AM-broadcast receiver right next to the primary receiver and tuning the "injection" receiver across the 530 to 1600 kHz band in hopes to generate a beat frequency. More often than not it didn't work, but I had some mixed success with that method.

I just fired up the NanoVNA set to a CW frequency 315.0 MHz and looked at the signal on SDRSharp using an RTL-SDR V4 SDR dongle, and the signal looked clean and was pretty much spot-on at 315.00 MHz.

Good luck with your experimentation. Good DXing.

Ken -- WB?OCV

________________________________
From: [email protected] <[email protected]> on behalf of Bruce KX4AZ <bruce@...>
Sent: Thursday, January 16, 2025 5:31 AM
To: [email protected] <[email protected]>
Subject: [nanovna-users] Use CW output as a BFO for SSB reception on a AM only receiver?

Has anyone ever tried using the CW output feature to generate a carrier for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only receive AM mode signals? It seems like this should be thoretically possible by attaching a small whip to the nanoVNA and placing it in the vicinity of the receiver. But probably tricky to get the exact frequency dialed in, as well as the signal strength relative to the sideband signals. Just seems like a fun radio exercise or for an emergency need.

Probably best to do it at the IF frequency rather than at RF.

73
Jeff G8HUL

________________________________________
From: [email protected] <[email protected]> on behalf of Bruce KX4AZ <bruce@...>
Sent: 16 January 2025 13:31
To: [email protected]
Subject: [nanovna-users] Use CW output as a BFO for SSB reception on a AM only receiver?

Has anyone ever tried using the CW output feature to generate a carrier for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only receive AM mode signals? It seems like this should be thoretically possible by attaching a small whip to the nanoVNA and placing it in the vicinity of the receiver. But probably tricky to get the exact frequency dialed in, as well as the signal strength relative to the sideband signals. Just seems like a fun radio exercise or for an emergency need.

There is an article in the August, 1963 issue of Popular Electronics
describing an external BFO. It attached to the receiver antenna terminal so
the idea has been around 60 years at least. I would imagine any modern,
stable signal source near the received frequency would work.

Dave N9ZC

On Thu, Jan 16, 2025, 7:17?AM G8HUL via groups.io <g8hul=
[email protected]> wrote:

Probably best to do it at the IF frequency rather than at RF.

73
Jeff G8HUL

________________________________________
From: [email protected] <[email protected]> on behalf of
Bruce KX4AZ <bruce@...>
Sent: 16 January 2025 13:31
To: [email protected]
Subject: [nanovna-users] Use CW output as a BFO for SSB reception on a AM
only receiver?

Has anyone ever tried using the CW output feature to generate a carrier
for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only
receive AM mode signals? It seems like this should be thoretically
possible by attaching a small whip to the nanoVNA and placing it in the
vicinity of the receiver. But probably tricky to get the exact frequency
dialed in, as well as the signal strength relative to the sideband
signals. Just seems like a fun radio exercise or for an emergency need.

Appreciate all the quick replies here confirming the BFO is do-able in theory. Easiest thing for me to try first would be the Gander VOLMET station on 13270 kHz USB, during the daytime, believe they transmit at 20/50 minutes past the hour. And the beauty of that frequency is the nice round number, great for the really cheap ($25 range) receivers with the 5 kHz tuning steps. In the past I've measure the nanoVNA CW output power at around -9 dBm, plenty to work with for air coupled "injection".

Separate from this, I've used the CW output in the past to fine tune outdoor matching transformers for receive only HF antennas. I would attach a short whip antenna and place the nanoVNA close enough to get a signal at least 10 dB above the noise floor....something around 50-100 ft away, and then evaluate the S/N ratio while swapping out matching devices etc. Worked like a champ for that.

Not as a BFO, that should work well. It does make for a good VFO going into a first mixer. getting the levels right can be challenging.

I use the nanoVNA to get my Hallicrafters S-40B receiver on frequency for a CW net when using it with my Elmac AF-67 transmitter on CW. I could easily set the nanoVNA slightly off the CW frequency I want to receive and use it instead of the S-40B BFO.

As suggested, it would be better for that application to use the IF frequency. That would allow tuning across a band without resetting the nanoVNA.

When I am using the nanaoVNA with the S-40B just to get it rather precisely on frequency so I can then zerobeat the VFO in the AF-67 with it, I can simply set the nanoVNA on the single wire that runs from the T/R relay to the antenna terminal of the S-40B. That injects plenty of signal for the purpose.

73,

Maynard
W6PAP