[Lowfer] Re-capped Heath HD-1420 MP and EAR before and after

[Michael Sapp]

Hi All: Here are the results of re-capping my HD-1420 VLF Converter.  I took a hint from W1VD's VLF 2N5109 preamps design and changed the .1uf input coupling and emitter bypass caps on the 2N3904 preamp of the HD-1420 to 10uf non-polarized.  In doing so, I discovered the .1uf emitter bypass disc ceramic only showed 1 M-ohm or so for a DC resistance check, which prompted my to change all the other .1uf disc ceramics as well. Most were in the 10 to 50 M-ohm range for DC resistance test. The new metal poly film .1uf replacements all measured over 2000 M-ohms for a DC resistance check.  Here is lowfer MP under daylight groundwave with a prior "typical" signal level peaking about -43 dB with the HD-1430 before any upgrades

http://s1296.beta.photobucket.com/user/wa3tts/media/MPFBRAT.jpg.html?sort=3&o=1#/user/wa3tts/media/MPFBRAT.jpg.html?sort=3&o=1&_suid=135118617183703727602925613689


Here is lowfer MP under daylight conditions after going to 10uf non-polarized caps for the HD-1420 preamp and other .1uf replacements with the mouse cursor over a -31.5 dB signal peak

http://s1296.beta.photobucket.com/user/wa3tts/media/mpoct23.jpg.html?sort=3&o=0#/user/wa3tts/media/mpoct23.jpg.html?sort=3&o=0&_suid=1351186759555045888838890786154


For a second example, here is lowfer EAR in daylight ground wave before the converter upgrade. In this capture the left side of the capture sequence was peaking -57 dB on my Northeast EWE and the right side of the sequence was peaking -63 dB on my Southwest EWE

http://s1296.beta.photobucket.com/user/wa3tts/media/EAROCT16_zps71d263d0.jpg.html?sort=3&o=5#/user/wa3tts/media/EAROCT16_zps71d263d0.jpg.html?sort=3&o=5&_suid=1351187243499011497139796519556

After the converter re-cap EAR is peaking -51.6 dB on my Northeast EWE, a 5~6dB improvement for daylight ground wave conditions:

http://s1296.beta.photobucket.com/user/wa3tts/media/EAROCT22.jpg.html?sort=3&o=0#/user/wa3tts/media/EAROCT22.jpg.html?sort=3&o=0&_suid=1351187435725010583303856551757


The VLF converter is also hearing much better in the 10 to 100 kHz range, with NAU on 40.75 kilohertz about s1 prior to the re-capping and S-5 tp S6 after the recapping, which turned out to be about a 20 dB improvement as measured by step-attenuators on the converter input. HWU in France on 21.75 and DHO in Germany on 23.4 kHz now routinely heard with the HD-1420 re-capped.

I did not have any 10uf NPs conveniently on hand, so I made some 10uf NP through-hole caps with some 1uf SMTs on a PC card and added wire leads. Best to tin the PC traces first and clean away the rosin to have a good high-ohm DC resistance check. These home made through-hole caps checked at over 2000 M-ohms DC resistance and with careful cap selection or adding / subtracting a chip cap or two you can match up a pair of 10uf NPs very close in value.

http://s1296.beta.photobucket.com/user/wa3tts/media/IMG_2522.jpg.html#/user/wa3tts/media/IMG_2522.jpg.html?&_suid=1351188191625045125496626946676


Anyway, I thought I would share the results as it was a good learning experience for me and some other Heath VLF converter owners out there might take a second look at this
particular 1980s~1990 boat anchor....

Thanks Jay, W1VD, for posting those 2N5109 LF VLF pre-amp designs on your web page and your VLF station list.

73  Mike wa3tts