Re: TXing on 30/40 with a 20m QCX: will I destroy it? #qcx

Alan de G1FXB

Hi Reiner,

No reason to expect any increased risk of destruction,
There is a US ham who has jumpered across the inbuilt TX LPF and runs all external filters in the coax.

I think he has two physical QCX's and uses them 80-10 metres with great success.
search the forum for the reports from Bill,
N4QA for the techniques


On 14/07/2019 12:42, DL8LRZ wrote:
I have now succeeded in modifying my QCX-30 with a switch to Duoband 30 / 40m. The occasion was the temporarily difficult conditions at 30m. The biggest problem was the small space in my home-made housing.
I acted like this:
The switch is an Augat ASE62R (DIP, 6 changer)
The built-in low-pass filter is connected in parallel with 4 capacitors. The blocking effect for the 2nd harmonic (14 MHz, approx. 44dB) differs only slightly from the 30m filter according to RFSIM.
In addition, the resonant circuit in the built-in antenna tuner (simplified Z-match) selects Rx and Tx
The RX circuit is connected in parallel with a capacitor + trimmer for exact adjustment to 40m.
The keying was not changed.
Result: good sensitivity on both bands, unchanged output power, now on both bands.
The VFO frequency is recalled from memory as the band is changed.
A first test brought a 40m-QSO.
vy 73 Reiner DL8LRZ

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