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Old 11th May 2021, 10:40 am   #41
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 378
Default Re: 'Proper' DAB conversion for valve radios

Review Part 1

OK, so the module arrived and I couldn't wait to open the parcel and install it.

First impressions; the unit is very well made and consists of a shrink wrapped module connected to a small unit which is mounted on a suitable valve plug. There is a flylead connected to a crocodile clip and a screened lead to an aerial socket. This teminates in an F plug, and a coax adapter is included which is a nice touch. Also included are installation instructions and a seperate operational guide which can be given to the end user if the set is not yours.

Remember, these are made for your specific radio. I suspect that the 'module' is the same every time, and that any changes to suit your radio would be on the valve plug board. Mine therefore included a suitable resistor to take the place of the series valve heater. Perhaps on some, the crocodile flylead would not be needed.

Installation is easy. Removed the mixer valve and insert the board. The flylead needs clipping to a suitable anode supply rail. You can of course remove the crocodile clip and solder the wire, but the idea is that the conversion is easily reversible. I noted that the crocodile clip is a good quality and will happily 'stay put'!

The construction of the unit appears to be very well made and the PCBs are excellent quality. I have removed the shrink wrap to take photos and see the construction, (as well as checking connections, see later). A quick reminder; while the set warms up, the unit scans for DAB (and DAB+) stations and stores a max of 100 in its EEPROM. Once stored, the unit only checks for new stations and there is a simple procedure for clearing the EEPROM if needed to start a fresh scan. The micro then spaces the stations out along your AM dial and you select them by 'tuning' your radio as before. The entire radio is used as the unit outputs IF.

I have some teething problems getting the unit to find stations which I am discussing with the developer; more later. However, the unit also generates 'static' hiss, which it inserts between stations. This is actually a nice touch. I also noticed a slight 'birdie' sound while tuning up and down. The whole experience is nice and tactile and the radio feels authentic.

The developer/engineer is Herbert, and his support is excellent, although he is not tied to his emails 24/7! I am working with him to resolve a tuning issue, so this concludes part 1 of my review. Part 2 will follow when it is working properly and I can give an overview of performance.

In a nutshell, despite having a good DAB signal where I am, the unit did not find any stations. After removing the shrink wrap and trying an aerial connection directly to the DAB tuner module, it did find some. It appears that the isolation transformer attenuates the signal too much where I am. I had even tried an external aerial. I will report further once this has been resolved.

Overall though - I am impressed so far, and for some, this will be an interesting adaptation to a vintage set. I have attached a few pictures of the unit.
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