Tag Archives: Radio Modifications

Imre’s HanRongDa HRD-737 modification increases sensitivity

Many thanks to SWLing Post contributor, Imre Olajos, who writes:

Hi, HRD 737 lovers! I have a good news!

I  (became brave enough to) modify my HRD-737.

I tried reverse-engineering- but I gave up. No numbers on IC-s. I found specifications for the analog switches (one for each band ) and found information about the transistors around those analog switch IC-s. Nice, 1 GHz fT transistors, all surface mount, so I gave up that line.

I found an NPN SM transistor in a damaged TV remote. It is only a 300 MHz transistor but
I had no better than that, so I started to build a little antenna amplifier circuit, wide band and simple.

I lost a few SM capacitors during the soldering but I have plenty of those. So the 1/4 square inch circuit board was finished last week. I tested it with an external 3 volt battery and I found it good working. Today ( 07-27-2019 ) I opened up the HRD-737 and wired it into the radio.
The results are much better than I expected. The HDR-737 became a good shortwave radio!

When I touch the built in antenna by my finger, radio is sensing the touch and station comes in. This effect was not there before. Radio became more sensitive on CB band than my Realistic DX392.

I have a YouTube channel [in the following video/slideshow] and I will show you the little ugly but great working circuit in the radio:

Click here to view on YouTube.

Later on next week I will try to record some video of the shortwave reception and post up it on the same YouTube channel.

I am a shortwave lover since 50+ years and I will be very happy to share the good news with others. Now I can listen my Greek music on this little radio, on 9420 kHz. Yes, the radio became [more sensitive than I had hoped].

You can see my other shortwave radios on my YouTube channel too, Have fun and never give up the hope!

Many thanks, Imre, for sharing and documenting this modification. One of the lessons here, too, is that if you have an inexpensive radio like the HanRongDa HRD-737 and you feel tempted to try a modification, there’s little to lose. It’s not like modifying a $1000 transceiver–just dig into the little radio and give it a go. If you harm the radio, you’ve only invested $37 or so in the project. That’s a much better solution than letting it sit on a shelf collecting dust because it’s not sensitive enough! Well played, Imre!

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Tivdio V-115: Simple modification to abate internally-generated noise

Many thanks to SWLing Post contributor, Marc Thomas, who shares a link to this site which describes modifications to eliminate the Tivdio V-115’s internal noise.

In a nutshell, the author made two small mods:

  • Decouple the power/battery with an electrolytic capacitor of around 10uF soldered to the battery connector inside the radio (see photo above)
  • The author also grounded the speaker, but didn’t test to see if this alone had any positive impact

I could not find contact details for the author of this mod, so I hope they don’t mind the fact I shared it here on the SWLing Post.

Note that the Tivdio V-115 is also known as the Audiomax SRW-710S and Kaimeda SRW-710S (and likely rebadged as a number of other models).

Click here to read reviews of this radio.

Retailers:

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Guest Post: A DSP Hi-Fi “Stupid Radio Trick”

Many thanks to SWLing Post contributor, TomL, who shares the following guest post:


Stupid Radio Trick – DSP “Hi-Fi”

by TomL

If you can remember the 1960’s, there was an audiophile rage going on called Hi-Fi.  The base unit consisted of a ponderous piece of furniture consisting of a rectangular cabinet and equally large mellow sounding speaker of fairly smooth frequency response, say in the range of around 40 – 15000 Hz.  They would have a built-in radio (using vacuum tubes) with large analog scale. Most would also have a “record player” embedded on the top to spin some vinyl discs (78 or 33 rpm).

For pedestrian consumers, it became a decision of how to keep up with the Joneses, so-to-speak.  And that meant a trip to Sears to look at the latest offerings. When the decision finally came to purchase, of course no one could buy it outright.  So, to add to the suspense, one had to put money down on “Lay-A-Way” plan that did not allow you to take possession of your prized choice until the last monthly payment!  One had to visit or mail in a check every month.

So where am I going with all this?  Well, as you can see from the photo [above], I have purchased three portable radios for three very different purposes.   All three were painstakingly studied and reviewed and weighed against all other possible choices. All are highly rated by the usual reviewers like RadioJayallen, SWLing Blog readers and other internet personalities.  The Sangean is for home use and listening to baseball games when I did not want to fire up the stereo hooked up to the Grundig Satellit 800. The small Sony ICF-19 is a phenomenal knock around radio for the car and listening while out to lunch or a walk in the park.  The large Tecsun S-8800 is a possible replacement for my ailing 20+ year old Sony ICF-2010 for shortwave use.

Well, I was tired of listening to any one of them in terms of sound quality.  The Sangean has too much upper bass/lower mid range, the small Sony is very carefully maximized for total speech clarity, and the Tecsun seems to lack a little in the mid range frequencies (compared to highs and lows).  Staring at them, I thought to self, “What if I turn on the Sangean and Sony together???” What ensued was a revelatory sonic experience (it sounded pretty good)! One seemed to fill in the other in certain ways. But it was not perfect.

Duh, I had the new Tecsun in a carry case while trying to decide if I send it back for a tuning quirk and dug it out and plopped it on top.  Turning it on, I heard more lows and highs, just like a Field Radio should have but with the mid range filled in! After very careful volume adjustment, I now have something that could rightly be called DSP Hi-Fi.  At least, that is what I am calling it for now. ?

Violin and piano pop-out of an orchestra but not too harsh sounding.  Rock & Roll sounds loud and punchy without that boombox effect. Bass lows are there (could be better, now all I need is a small subwoofer connected to the Tecsun line-out ???).  Highs are there too but well controlled. Mid range voice clarity is stunning, as if someone is in the room with me but not sounding too forward! It is not room-filling but acts more like a near-field monitor.  I like that I can line-up the speakers over each other.

The really fortunate thing is that all three radios have complete DSP for FM and receive my favorite over-the-horizon station with very similar reception quality.  Also, they process DSP with a similar delay before output to its respective speaker. The sound is fairly coherent and even though it is still mono output, the full range of musical fidelity can be appreciated better.  It is not audiophile quality but it is very satisfying and I can actually hear more details in the music than with any one of the radios by themselves. Just goes to show you that you CAN teach a new Radio dog old Tricks (LOL)!

Happy Listening,

TomL


I love it, Tom!  Thanks for pointing out that sometimes it takes a “stupid radio trick” to really produce some amazing audio fidelity! This reminds me that in the early 90s, I used to have a Zenith Transoceanic and RadioShack DX-440 on my radio table in my room.  If I recall correctly, the Zenith was on my left and the DX-440 on the right. I used to tune to shortwave, MW and FM stations and produce a makeshift “stereo” effect by playing both at the same time. Sometimes, on shortwave, it actually helped me discern voices in weak signal work!

Thanks again, Tom!

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