HERESY ... Anyone Using an SDR Receiver on AM ?

[W1KSZ]

Given all the noise associated with AM Reception, I was wondering how an SDR Receiver
would work as an AM Receiver.

Anyone using one now ? Contact me off-list to avoid the brick-bats that may result.

Thanks, Dick, W1KSZ

[KB2WIG]

Now you have done it. Double secret probation for you.


KLC

[w1vtp]

I know of several (or make that many) stations that are using SDR technology as receivers.  My class E station uses a Flex 1500.  All SDR receivers use synchronisys  AM detection which is a form of enhanced carrier detection.  This mode works particularly well during deep selective fading.

Noise reduction?  I'm not sure SDR technology handles noise reduction much better than modern "boxed" transceivers.  Others on this forum may have some anecdotal experience with noise reduction.

Al

[KA0HCP]

No heresy in using SDR radios for receiving OR transmitting AM. 

They work perfectly fine.

BTW, the purpose of a forum is to share information.  Posting a question and then moving to email undermines the function of forums.

[kb3ouk]

Using an SDR as a receiver, heck there's plenty of them being used as transmitters too, and they're some of the best sounding rigs on the air, next to a broadcast transmitter. I've considered using one with my home brew 814 transmitter once I get it finished, just need to figure out a method of transmit/receive switching (and actually get something decent to use as an SDR, I've played with the rtl-sdr dongles but that's it). It's a myth that AM is for vintage gear and vintage gear ONLY, there's just as much modern stuff/technology on the air now as there is old stuff. Even my transmitter I'm building is not what I consider even close to vintage or vintage like, it's a mix of vintage and modern parts, more of what I could get my hands on instead of being period correct, the modulation transformer is a 1930s Inca unit, while underneath the chassis of the RF deck lurks a brand new Antek toroidal transformer for the 814's plate voltage. Honestly, most of the SDR radios out there run circles around all but maybe the very best vintage receivers, and with prices like they are for the old stuff, probably cheaper too, also considering your vintage receiver you just bought might need a ton of work to get running, where the SDR works right out of the box (most of the time).

[Pete, WA2CWA]

If you go back to the AM Rally in early April, here is a SDR rig tally of active operators:
Flex 5000: 19
Flex 1000: 1
Flex 3000: 8
Flex 6500: 9
Flex 6300: 11
Flex - Unknown: 15
Anan (Apache Labs): 3
IC-7300: 36

There are a number of features and applications within SDR-type receivers/transceivers, that would run rings around some of the older boatanchor receivers. Most of the noise reduction techniques used in this equipment are highly effective but a lot depends on the type of "noise" that you're trying to reduce or eliminate. Remember that atmospheric-type noise is a lot different then your typical ignition, power line, motor noise, vacuum tube noise, etc. When trying to reduce atmospheric noise, most times the strength of the signal you're trying to receive, will also be reduced so you have to be careful here. There are also outboard digital noise filters like the Timewave DSP-599 that are also effective for reducing all types of noise.

[KQ6F]

I've been using both homebrew and commercial SDRs on AM for several years.  Using them exclusively. There are several reasons:
 
1)  Superior brickwall filter characteristics that can be adjusted with a mouse click.
2)  In most cases the noise blankers are more effective owing to digital look-ahead techniques
3)  Superior synchronous AM demodulator
4)  Superior panadaptor that displays activity on a major part of the band.
5)  Audio quality limited only by the amplifier and speaker of choice
 
Of course there are no conventional knobs to twist or meters to read, and that may be a problem for some....

[AG5CK]

Being able to adjust the bandwidth of the upper and lower sidebands independently is wonderful when some guys on lsb park a kc above you.

With powersdr you can narrow the upper sideband to silence the qrm and still hear the full bandwidth of the lower sideband. I haven't figured this out with any software I've used with the sdr play but the brick wall filtering still helps tremendously.

[kb3ouk]

Being able to adjust the bandwidth of the upper and lower sidebands independently is wonderful when some guys on lsb park a kc above you.

With powersdr you can narrow the upper sideband to silence the qrm and still hear the full bandwidth of the lower sideband. I haven't figured this out with any software I've used with the sdr play but the brick wall filtering still helps tremendously.

That also comes in handy even when another AM station fires up only 5 khz away, pull the sideband towards them in so you don't have to listen to the garbage from their sidebands.

[KD6VXI]

HDSDR has a killer RF noise blanker.

The IF banker, doesn't do much.

The rf blanket will take my noise level down almost 6 s units.

My Kenwood doesn't do nearly as well.

--Shane
KD6VXI

[w4bfs]

maybe get just a little more specific ....

lets say a Collins 75S1 which is a nice bare bones type of receiver ...  I would like to integrate a SDR into the 455kHz if chain, let it do its magic and then drive the avc and audio out .... Is there any sort of SDR out there to do this ?

[w1vtp]

maybe get just a little more specific ....

lets say a Collins 75S1 which is a nice bare bones type of receiver ...  I would like to integrate a SDR into the 455kHz if chain, let it do its magic and then drive the avc and audio out .... Is there any sort of SDR out there to do this ?

It is very doable.  I've done it.  That's how I heeded the clarion call of a full fledged SDR transceiver and got the Flex 5000.

All you need is the free software, a computer that is adequate (most modern computers are adequate) a mixer (I prefer a double balanced mixer. See link below for this) and a good signal generator that will serve as an LO to bring the output down to the sound card frequency.

Very doable, Al

http://www.ebay.com/itm/HP-10534A-Mixer-/272648353505?hash=item3f7b1bb6e1:g:Rd8AAOSwKfVXLhHK

[w1vtp]

I just checked the manual for the 75S1 and I do not see an IF output.  So unlike the SP600 and the SX73 which do have a IF output, one would have to dig into the circuit and cathode follower the IF output to the outside world - for isolation and matching purposes.

Al

[WD8BIL]

Hey John (Beefus)

I have a 455kHz SoftRock I.F. converter card that is spare to me. If your address is good in QRZ I'll send it out.
Power SDR software can be downloaded in many places.

The only thing you need to consider is the input of these things are 50 ohms and they'll load down the I.F. ifn there's no buffer stage 'tween'em.

You're welcome to it!

Buddly

[w4bfs]

thanks Buddly ... contact info in QRZ is fb .... thanks John

found Jay's R390/Softrock SDR combination article: http://www.w1vd.com/R-390ASoftRockdetails.html