[Linrad] MAP65 + Linrad hardware

["Alex Artieda" <emeham.com; hb9dri@xxxxxxxxxxxxxxxx>]

Hi All,

Having two down converters for Adaptive polarization (with the same LO) is
not complicate to build, at the moment I'm using the WSE converters of Leif
and I'm in agree with Jeremy W7EME, in combination with Linrad they are the
best RX receptor I try in 25 years, even better than my YAESU FT-1000MP Mark
V.

A very simple approach will be to build your dual down converter based on
the famous SOFTROCK kits, I did very simple:

- You need to decide first your IF frec. Because I had in stock a 130MHz
crystal I decide my IF in 14 MHz (my input will be 144 MHz)
- You order 2 Softrocks V6.2 BUT with the right crystal for the properly IF
you already selected.
- Build both Softrock receptor without the oscillator part and build only
one oscillator in a small circuit board, send the RF output of the
oscillator to a simple resistive divider (Wilkinson splitter) and then feed
both softrock unit with the same coaxial length.
- Now the front-end part, you need two TOKO input filters for 144 MHz, the
144MHz antenna will be direct to the input of one filter and then you will
put a MMC amplifier like MAR6 between the output of the first TOKO filter
and input of the second TOKO filter, the you install a -3dB resistive
attenuator after the last TOKO filter and the send the signal to a MIXER
like TUF-1H, the resistive attenuator is to keep the impedance in front of
the mixer in 50 ohms, the output of the mixer go direct to a DIPLEXER, is a
simple filter with one resistor, to capacitors and one simple coil (values
depend of your IF). The output of the diplexer go to another MMC MAR6
amplifier and then finally you have your RX output in my case in 14 MHz,
this output go into the RF input on the 14 MHz softrock receptor, this
explanation is multiplied by two because you need two channels identical.
- THE LOCAL OSCILATOR: forget to use any kind of DDS (direct synthesizer
Oscillator) the HF guys are using with the softorck receptor, any kind of
hoe made PLL or digital synthesizer produce a big amount of harmonic and
birdies specially in IQ receptors. You need to build a EXTREM LOW PHASE
NOISE oscillator and this is very easy following the instruction on the Leif
homepage, the LO need to have and amplitude of aprox +20dBm because the
TUF-1H mixers need +17dBm. The output of the LO is divided via a Wilkinson
splitter and introduced on the TUF-1H mixers with the same length of coaxial

The result I said is "not only good" is "very good", if you are able to
build some small circuits this is the perfect project for you, in the same
way I already build a dual down converter for 432MHz, unfortunate Leif WSE
converters stop in 144 MHz, following the same principle but without the
softrock units I build a dual down converter with the input in 432Mhz and
with the output in 70MHz to feed directly the second WSE down converter of
Leif we have in HB9Q... and works perfect.

The Adaptive polarization works fine and if you build both oscillators and
the front-end part following the standard practices for this frequency you
will enjoyed a complete new world together with LINRAD and MAP65, the system
is extreme useful in CW also but unfortunate the number of  active CW
stations in CW is very low at the moment.

Well I recommend this solution if you cannot pay for a WSE converters, the
Linrad homepage give to you a lot if ideas about this kind of IQ receptors,
I think most of the people with WSE converters in some part start before
playing with the softrock receptors and I recommend that.

Best regards to All, 

73 de Alex, HB9DRI





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