Radio Shack DX-440 (ATS-803) Success!

[tedex]

After installing the mod, using Dream, and much tuning and waiting for an optimum signal for a couple of nights, I was rewarded with a nice 15 minutes or so of 7370khz Vatican Radio clean audio on Saturday evening (12/23) at just after 2300 UTC.

Best SNR was 13, S9 signal, 10m longwire antenna with an MFJ-945E tuner, the radio modified with the I5XWW 455khz to 12khz board, although the DX-440 uses 450khz IF, it works fine. Also picked up some intermittent audio from 6080khz CRI a bit later, just after 0100 (12/24), with SNR of 12 and S9+ signal.

SNR 12+ seems to be the key, regardless of signal. QSB is brutal.

PC used is a HP NX9110 with desktop dock, and it uses the Soundmax embedded audio. In fact, I am able to run SDradio simultaneously and listen in to the signal unless using the Dream audio record setting.

Reception is rough here in South Texas. I have high tension lines a mere 100ft. from my location and antenna.

[fibber]

I have one of those as a bedside radio. I have thought of mods for it but haven't yet burned my fingers with the soldering iron on that one. The I5XWW boards are great aren't they! Be sure to post your mod comments and experience on DRMNA.

You should have good copy on RNW via Montsinery 15425khz @ 2200z. I'd guess an SNR of 23 or better.

PS. I do the same with SDRadio. I mute and minimize it unless it is needed.

Merry Christmas from the North West!
-Christopher

[tedex]

what's really maddening is that I can copy the banners and station ID's for a lot of broadcasts, but the SNR just won't cut it for audio. I'm going to try a loop antenna next, just debating on whether to buy or build it first.

Sackville comes in here always, but, amazingly, the signal is just not good enough to get audio.

I plan to get another mod board and try installing into a Kenwood TS-140S into the empty Narrow filter slot.

ALso, I'm getting a Coding Technologies DWT next week, so maybe that will work out better.

[simone]

Hi tedex,
I had also modified an ATS-803, the SNR I achieved was about 25dB, so not really high but good enough for decoding on nearly all transmissions.
Can you please post a screenshot of the input spectrum and the SNR/MER plot from Dream?
Simone

[tedex]

Hi tedex,
I had also modified an ATS-803, the SNR I achieved was about 25dB, so not really high but good enough for decoding on nearly all transmissions.
Can you please post a screenshot of the input spectrum and the SNR/MER plot from Dream?
Simone


here you go.

[tedex]

here you go.

input spectrum

[tedex]

input spectrum
another shot. was getting intermeittent audio on this one

[simone]

Thanks for the screenshots, basically it looks like a poor signal and not a problem with your setup (soundcard/ Rx), so maybe you could try to improve on the antenna. However your IF frequency is a bit high, no problem with Dream but it would not work with FhG software. Also seems the IF is not very stable, there is a difference of 2 kHz between the two attachments.
As fibber says reception of RNW from Montsinery 15425khz might give a better signal.
Simone

[tedex]

tnx. I may have been switching the BFO in and out in there somewhere ;-) Actually it started coming in ok after a bit on RCI 9800. 15425 was there, but no audio. I may need to go back in the radio and shortent eh leads on the IF tap. THey are only about 40mm now, but I may replace with shielded cable and put some ferrites on.

[simone]

I just remembered that the gain had to be adjusted very carefully with this radio, maybe you already did that.
Simone

[tedex]

also, the IF is high because I have yet to swap to the 465 crystal in the converter board. I can shift it down with the BFO, but it doesn't really work any differently.

So, overall, the inital experiment seems to be successful.

SO, also, of note, the fact that I actually get better performance with the notebook powered by supply rather than battery. Also, no difference between running the radio on battery or on PS.

I will, in addition to cleaning up the IF connection, put in a DC blocking cap on the converter output so I can do away with the isolation transformer I have between the converter output and the notebook mic input. That may give some improvement.


Signal strength. Well, now that's a different story. I can receive these stations full scale+, but the noise level is mostly horrendous. I have power lines very close, and the irony is that I chose this townhome location because it has a thrid floor loft, my radio room, and that gave me a high balcony from which to hang some 2m and 70cm antennas, and a 10m dipole. Unfortunately, having a 30ft longwire, horizontal, 30ft. off the ground (lying on the tile roof) is not optimum. Too much noise. It would be better lying close to the ground, but I have no way to do that.

I will likely need to try a loop antenna. I have a couple of designs in mind.