Disable tx in hardware ie jumper

[Albin Stigö]

Hello,

Is there a simple way to temporarily disable tx? I want to use my HL2 with an active loop antenna and need to make absolutely sure I don't accidently transmit into it. Is there a jumper I can set to disable tx?

Albin SM6WJM

[DL1YCF]

I am not hardware guru, but the main PA current goes to the

center tap of transformer T3 and that comes from „VPa“.

If there is no VPa to the center tap of T3, the finals get

no power. VPa (8 Volts) is generated from the main Vcc

on page 2.

My guess is if you cut this (or transform it into a jumper),

this make the desired hardware „cut off“ of the PA. Of course,

there may be other solutions (bias, or RF input).

I forward this to the list if there are further comments.

Am 27.08.2021 um 11:27 schrieb Albin Stigö <albin...@gmail.com>:

Where's the best place to do that?

On Fri, Aug 27, 2021, 11:08 DL1YCF <dl1...@darc.de> wrote:

cut the power to the finals.

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[Sebastien F4GRX]

According to schematic setting CN8 open will inhibit transmit at gateware level.

Found it the hard way when soldering my own board, because I forgot the associated pullup and transmit was intermittent.

https://raw.githubusercontent.com/softerhardware/Hermes-Lite2/master/hardware/hl/hermeslite.pdf

Sebastien

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[Alan Hopper]

There is a Rx only input you can take off the connector between the hl2 and the filter board.

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[Josh Logan]

I would suggest loading the 10rx gateware.

variants/hl2b5_cicrx - 10RX only gateware for Hermes-Lite 2.0 build5 and later. This only supports 192kHz receivers. This uses only CIC filters and consequently only about 70kHz of the spectrum is usable. This is for multiband skimming.

Not only is tx disabled, but you can monitor more bands at the same time.

SparkSDR is the easiest software to setup receivers on that many bands.

When you want to transmit in the future load the hl2b5up_main.rbf gateware.

73, KD7HGL

Josh

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[Anthony N1IG]

this thread might be of interest:

https://groups.google.com/g/hermes-lite/c/smggsLCfVuY/m/gP9wYQQBAwAJ

[Jean-Baptiste GALLAUZIAUX]

If you are using Thetis v.2.8.12 beta 5, in "Setup" "H/W Select" menu there is a box "Receive only" which you could select?

73 - Pierre - FK8IH 

[DL1YCF]

I think all the suggestions of this kind miss the original question.

As far as I understood it, the question was how to disable TX such that

it cannot be activated by the software, no matter whether it is

a user of the software who wants start TXing or whether it is a software

or gateway running havoc. Therefore the original question alluded to a

„jumper“, and I think this must be in the VPa or Bias lines.

However,  a receive-only gateware (as suggested here) might be OK for

the original poser.

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[dick_...@hotmail.com]

There is a QST article  August 2018 pp. 32 - 35 by John Hurst KU6X called TRS Switch that covers this type of application.

I have some redesigned PCB's on my site http://www.k9ivb.net/KU6X%20TRS/

Also John has much more data, simulation and application  information on his web site https://ku6x.com/solid-state-tr-switch-additional-info/

There are SMD and through hole designs. 

Worth a look if you want to use a stand alone SDR receiver in conjunction with any other Xceiver or high power amp.

Dick K9IVB

[Steve Haynal]

Hi Albin,

As others suggested, you can install a jumper at CN8 to inhibit transmit. This is still implemented in the most recent gateware.

The LDMOS devices used in the HL2 PA are very hardy. I don't know of a case of someone ruining the devices with a very bad SWR. TX automatically stops if the temperature is above 55C which offers additional protection.

73,

Steve

kf7o