QRO 160 / 80m remotely controlled PA by OK7GU (2011)
For my remotely controlled QTH I needed a robust, reliable, remotely controlled powerfull PA for 160 and 80m. The best way to get one was to construct a PA by myself….
After some time I evolve this unique product: – Using 2pcs of SRS457 reliable robust tubes, Ua=5kV, Ia=1A, 3kW out – 100% Remotely Controlled with On/Off switching, heating, band switching (160m, 80m CW, 80m SSB) and remote indication
Robust Power Supply with 3 powerfull three-phase (3x400V) toroidal main transformators and six-pulse bridge rectifiers, no elyts
For those who are interested see more pictures on my Facebook Pages
XV432 Elecraft transverter modification (2014)
The original ELECRAFT XV432 transverter is from the technical view not a good product.
Two main problems exists:
1. In the original version the X-tal oscilator stability is bad with big temperature drift +-3kHz!
2. The originaly used PA modul Toshiba S-AU83L is designed for FM modulation, not for SSB.
SSB signal from XV432 is distorted, badly readable.
The original used crystal 134.667MHz should be replaced with the new high accuracy crystal + option, delivered by Elecraft.
The Crystal Oven, delivered by Elecraft, should be used, too.
The original oscilator circuit diagram is a very old design with bad oscilator spectral purity. The XV432 with this oscilator generates large spectrum of not desired products and the frequency is unstable. This was a reason that I totaly changed the oscilator diagram, using the modern J310 J-FET.
After this change the XV432 is stable with perfect spectral purity.
J-FET J310 should by used only. Similar FETs (BF245, 246, 247 etc. works NOT)
The original S-AU83L FM module, delivered by Elecraft, should be replaced by a linear PA module. With the original S-AU83L the SSB signal is totaly distorted.
I changed this FM module with a linear Mitsubishi module RA13H4047M (400-470MHz, 13Watt, 12.5V) with the same PIN connection. This new module works fine, the output SSB signal is pure and linear. After this change I can drive the solide state PA (about 8W of drive power), the PA deliver over 350W output at 432MHz.
The output signal is now perfect and the SSB modulation is fine.