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4m homebrew
Graham KimbellG3TCT
Why 4m homebrew?
● the only commercial rigs are– FM mode– Yaesu FT847
Why 4m homebrew?
● the only commercial rigs are– FM mode– Yaesu FT847
● A challenge (but not too much)
Why 4m homebrew?
● the only commercial rigs are– FM mode– Yaesu FT847
● A challenge (but not too much)● “4 is the new 6”
Recent dx on 4m
26 Jun 07 - G7CNF to VE9AA 4/6m xband 4626km
12 July 08 – CT1HZE to W3EP 4/6m xband 5334km
12 Jun 09 – SV2DCD to D44TD 4964km - 4m 2way Es record
What you need
● Transverter● PA● Harmonic filter● Antenna
● And a 28MHz transceiver of course!
Transverter options and costs
● DF2FQ tvtr – 4w o/p, 149Euro
● Spectrum tvtr – 25w o/p, £280, kit £179
● OZ2M - 0.1w o/p, 900DKK (~£106)● OZ2M - 25W PA, 975DKK (~£115)
OZ2M website
● Descriptions, schematic, performance graphs● alignment instructions, component lists● photos of built systems● data sheets for devices● ordering information
● http://rudius.net/oz2m/70mhz/transverter.htm
The OZ2M transverter kit● Professionally made PCB with solder mask and
silkscreen and 100% ready for use● All components to be mounted on the PCB● Metal sheet box● Four BNC coax connectors
The OZ2M transverter kit - 2
● Transverts 28MHz to 70MHz● Tx
– 100mW output, with PA module =>30W– 28MHz drive = 30uW to 1mW– spurious suppression -65dBc
● Rx– noise figure <2.5dB– IP3 = 7dBm
Receive response
Transverter output spectrum
The 70 to 28MHz spurious problem
3 x 42 = 1262 x 28.001 = 56.002and 126 - 56.002 = 69.998
Measured close-in spectrum
● Tx on 70.001 => 6000Hz● Spurious would be at 3000Hz● Level more than 80dB down
Construction
30W PA module - pcb
30W PA module - pcb
How to buy
● Email OZ2M to check availability● Send the required amount in DKK or Euro to
OZ2M (details at his website)– get the form from your bank “Sending a Relay
Payment Abroad” ; fill in and give to your bank– OR send the money via PayPal
● email OZ7IS with your requirement and delivery address
160W semiconductor PA
● Design by GI0GDP – 4m website● SD2931-10 RF MOSFET● 160W o/p from 50V● Schematic – my website
How to produce a schematic and/or pcb design● Program from www.expresspcb.com ● schematic capture + pcb design● customisable, includes library of components, can
be linked● free!
PCB design
160W semiconductor PA
160W PA – what you'll need
● SD2931-10 / MRF151 ~ £8-10 on eBay● enclosure – eg Maplin● fans – various● antenna c/o relay – eg S2 from Barend● 50V @ 6A PSU● power meter
Antenna options (horizontal pol'n)
● Buy one – eg Vine antennas● Build one
– dimensions from eg DK7ZB website– aluminium from Metals4U or Aluminium Warehouse– element clamps from (eg) www.nuxcom.de
● 3 ele: 60 inch boom, 6dB gain● 6 ele: 16ft boom, 10dB gain
More information:-
● Local oscillator temperature stability – crystal heater
● Stabilising PA quiescent current● Harmonic filtering● PA fan control
● www.g3tct.co.uk● www.70mhz.org
