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Old 02-21-2015, 02:17 PM
dewdude's Avatar
dewdude dewdude is offline
i <3 my Denon
Join Date: Oct 2006
Location: Manassas, VA
Posts: 112
So I've had an SDR for a couple months...

Hey everyone,

I know this is an amateur radio forum; although it does talk about DXing and I've seen a few things related to that....and I can't figure out if this fits in a specific category; plus I wouldn't mind hearing what you guys have got to say.

Going back to the beginning: A few months ago I started fooling around with a couple of AM tuners as I enjoy AM (and SW) DXing; threw up a couple of wires for antennas and played around. I then got more serious by stringing up 212 ft (61m) of wire for the job. I then started playing around with an old Panasonic boombox with cheap SW section on it and really started to miss the RadioShack/Sangen DX398/ATS909 I had years ago but sold when it was apparent BPL was making that useless. That's gone, so I started looking again. So I wrestled with the idea of getting one of the Tecsun units, as a new DSP based 909 was out of my budget. That's when I got to looking at RTL-SDR.

For those who don't know what RTL-SDR; basically some clever hackers/programmers/developers figured out you could make a cheap dongle designed for DVB-T reception act as a general purpose SDR. You're quite limited by the out-of-design use of the Realtek DVB-T chip; but you are able to get up to a usable 2.8mhz of bandwidth; although the ADC only samples the I/Q data from the tuner at 8-bit. It's still better than a lot a of cheap radios. But I got to looking at what you could do with the things and all the various software...and it looked like the most high-tech complicated radio ever! The waterfall display, the multiple decoding modes; there just seemed to be so much more flexibility in how I can tune the signals than I'd get with a hardware radio.

I wound up buying a RTL-SDR bundle since I wanted to go HF; the dongle by itself won't tune below 24mhz (sometimes down to 3 if you're lucky and use new modified drivers for some software), so I added an upconverter to heterodyne 100khz - about 40mhz up to 125mhz; also got the 1:9 balun the comany sold specific for longwire setups. I got all this a week before christmas; so I've actually had a chance to pay with it. My entire out-of-pocket cost was just under $100; a bit cheaper than the better TecSuns and far far more capable (the tuner in the dongle will go as high as 1700mhz).

Guys, this has pretty much really changed how I look at radio. For starters, the ability to tune 100khz - 1.7ghz (even if my sub AM BCB performance is crap) is just...mind blowing. I thought my 909 years ago with it's ability to tune from 150khz to 29.999mhz continuously was cool; this just blows it away. Being able to "see" a nice visual of the spectrum and signal is just outstanding too; I can for example what sideband an AM station has noise on it. That brings me to the IF filter; you can make that puppy almost as wide as you want; plus you have a fine adjustment so you can pick how much of each sideband you want. Of course, my favorite feature has to be "I/Q Baseband recording", where you record the entire I/Q stream that's being piped in to the software so you can work with it later. No more hoping I've got the thing tuned right when I record an audio sample; just record the I/Q stream and spend all the time you want tweaking tuning for a good intelligible sound clip.

Anyway, this thing has just been entirely cool for not costing more than it did. I can scan VHF, UHF, microwave, pipe the audio in to other programs for decoding digital modes, decode digital voice systems..I actually made a small quarter-wave ground-plane antenna for the 1090mhz ADS-B transponders and was pickin up planes 30k, 40k ft up sometimes 60 miles out (my sky view is horrendous and expected nothing out of ADS-B).

Of course, I just love the fact I can open my IF up to 20khz and get some pretty decent fidelity out of the one or two AM stations that broadcast music; yes it'll do that nifty FM Stereo and RDS stuff (I've actually been able to decode SCA with it) and maybe DAB if you're lucky enough to have that (no, no HDRadio).

Anyone else out there played with it any?

Denon PMA-770 - Sansui SE-8 - Akai GX365D - M-Audio Transit USB - DCM Timeframe TF400s - Bose Triport TP-1A
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