Tecsun PL-310ET - MW/LW Antenna Coupler

After carrying out the external antenna connection modification to the PL-310ET, I built an external antenna coupler for MW and LW.

The coupler uses (obsolete) Toko 10mm inductors which are tuned on the primary side by the varicap diode on the SI Labs IC. The secondary side provides a low-impedance coupling to an external antenna.

MW uses a Toko RWR331 230-300μH primary, 1.75μH secondary.

LW uses a Toko 98299 2.9-4.0mH primary, 46μH secondary.

Some excellent results have been achieve, particularly on Long Wave.

Comments

Tecsun R-9700DX Teardown

I've seen a lot of favourable comments on this analogue SW radio via various YouTube channels, along with it's sibling the R-9710. Sold in some (USA?) markets as the Grundig Yacht Boy 250. Exact specifications and schematics have evaded me so far, however I did find a teardown and comparison at RadioIntel.com from which I've borrowed this photo: Photo from http://www.radiointel.com/review-review-tecsunr9700dx.htm It appears to use dual-conversion on shortwave with a fixed crystal local oscillator (see the 10 crystals above the bandswitch). One feature is that the tuning on the short wave bands tune the opposite direction to the AM and FM bands. Here's my (incorrect) guess of how it works. AM band IF is 450kHz (from the orange block filter) AM local oscillator tunes 975kHz - 2160kHz. The image of the AM band (1425kHz - 2610kHz) is used as a tuneable first IF for the shortwave bands. Each band is 600kHz wide so it probably uses 2000kHz - 2600kHz. The SW ba...

Tecsun R-9710 Teardown

Although I've been itching to get my hands on the Tecsun R-9700DX, I wasn't really aware of it's smaller sibling, the R-9710 until I saw this review on the Two Hands and a Radio YouTube channel. Two Hands made the observation that the shortwave bands tune in the opposite direction to the AM and FM bands, which made me go and do a quick check other Tecsun analog radios. I found the R-9700DX also has this inverted tuning feature so some Googling later and I've located a teardown of the R-9710 plus other sets. The original article is in Chinese but you can view it through the magic of Google Translate . R-9710 teardown from http://www.leowood.net/sbdp209.htm Note it has eight crystals around the bandswitch for that fixed-crequency first local oscillator. Add the schematic found at http://www.fmdiy.com/ReadNews.asp?NewsID=305 More dead links to maintain unfortunately.

Tesco RAD-108 AM/FM/Shortwave portable radio review - American Style

I sent one of the RAD-108s over to Two Hands and a Radio for a YouTube review. Update - looks like 2H has taken his YouTube channel down so this is no longer available. Here is mine, a poor substitute. It didn't do too well on the American AM broadcast band, probably due to tuning in 9kHz rather than 10kHz steps!

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