13cm upgrade – SG- Labs Rx/Tx and Split Mode

In a patch of settled weather, I took down the jockey pole with its 13cm Wimo antenna and the 13cm box, so I am off that band for a while. I’m intending to modify the SG-Labs transverter for “Split Mode” operation and to add amplification on receive and transmit.

I was surprised how much muck had accumulated in the box, the only holes in it being the gap between the grommets and the cables (I hadn’t bothered with sealant) entering the box & little bleed holes underneath for releasing condensation. The chromed steel lid of the transverter had a few rust pocks on it, presumably from condensation, but internally, the transverter was fine with no condensation damage. The local birds sit on the aerials & the boxes & do what birds do. I’ve given the box a good clean.

G3YJR_13cm_jockey_pole_box

I’m planning to take out the transverter and put a Band Pass Filter (BPF) in the box, together with a coax relay & a pre-amplifier for receive and then to have separate coax cables up the pole for the 13cm transmit and receive lines. I believe a BPF is necessary to protect a wide-band pre-amp from cross-modulation effects. The Crosspool transmitter towers are very close and line-of-sight. Also, on transmit, it is important that other users neighbouring the radio amateur band do not receive interference from minor spurii, boosted by the linear amplifier.

This little box has worked well up on the pole, with contacts up into Scotland (to Jon GM4JTJ) and down to the South and to Denis G3UVR over the Pennines. It even managed one contact with Frank PE1EWR in Holland, so it has done well with its 2W output.

In the lab, I’ll mount the transverter in a box with a sub-band switch for selecting the Local Oscillator frequencies,  a switch for internal/external reference oscillator (the transverter does not default to the internal oscillator when the external input is missing – it flashes a little red light!), some monitoring LEDs, and a power output (maybe SWR) meter. I’ll add an Andrews linear amplifier indoors (it is too big a lump for the pole) with a sequencer to control the amp. and the relay up on the pole.

I intend to find a way to select 2W (the current output), 10W or 25W output for the various contest restrictions and full power (100W?) for long distance (DX) contacts.

I’m aiming to activate 2300 MHz as well as 2320 MHz (with the possibility of 2400 MHz) with some amplification on the output and pre-amplification on receive.

The picture shows the board layout near the relay, still arranged for “Rx/Tx” mode, (both receive & transmit route via the upper SMA connector on the left with the strip into), before modification for Split Mode (receive via the lower SMA, in the bottom left-hand corner of the picture).

The brown & orange wires were for forward & reflected power monitoring in the lab.

Note the little “0” ohm chip “resistor” by the orange wire. In Rx/Tx Mode, this routes the receive input away from the relay:

G3YJR_13cm_Rx-Tx_mode

Update 31-December_2018:  The “resistor” has been moved in the picture below so that the Rx input now comes straight from the SMA socket and by-passes the relay.

dscf9285

 

One thought on “13cm upgrade – SG- Labs Rx/Tx and Split Mode

  1. Pingback: 13cm SG-Labs transverter | g3yjr

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