rf1-ant power

[Luc Laureys]

Hey,

i playing around with both connectors..

so now the question..

witch settings are correct for low power output on connector rf1

want to use it for duplex..separated rx and tx antennes...

Grts

Luc

[Steve Haynal]

Hi Luc,

At a low level communicating with the Hermes-Lite, you need to disable the PA and the TR switch. There are two control bits for that. I'm not sure how they are controlled from various software. Please share which software you are using.

73,

Steve

kf7o

[Luc Laureys]

So i use the thetis hl2 software...and if rf1 give output i have always 5wtt output on this connection...

i did a mod for my ic-735...i have now a hf-rx output...(no if output!) and a pa-tx input to the ic-735 pa.this configuration give me abbt 125wtts with the hl2

so i think if everything go ok...i can have a separated rx and tx connection on the hl2...(rf1 for tx and ant for rx)

if not..i must make a rx/tx switch via the ptt....i hope not...

link to mod:

https://github.com/dl9lj/icom

Grts

ON7KEC - Luc

Op maandag 9 februari 2026 om 05:47:43 UTC+1 schreef Steve Haynal:

["Christoph v. Wüllen"]

According to the HL2 schematic, there is a relais U10/U11 which routes the RF output
either to the PA (TXPAp/TXPAn) or to the RF1 output, and this relais seems to
be controlled directly by the FPGA output "n1".

There is further FPGA output "p3" with enables/disables the PA via VBIAS.

And then there is third FPGA output "v1" which operates the T/R relais via INTTR.

According to the protocol, ADDR=0x09 bit=19 seems to control VBIAS,
ADDR=0x09 bit=18 disables T/R relay if PA is off, but I have to guess that
disabling the PA will route the output to RF1.

The question is, however, how to set these bits. In the original HPSDR
protocol, ADDR=0x09 bit 18/19 are the "Apollo" bits which are
hi-jacked by the HL2 protocol, so it depends on the HL2 support
in the software whether these are actually used.

I can speak only for piHPDSR, here, only ADDR=0x09 bit=19 are set
when the PA is enabled, and ADDR=0x09 bit=18 is always cleared

ATTN: this should be changed, namey to disable TR relay
if PA is off. I cannot speak for Thetis.

But I must make a measurement to verify if RF1 gets the RF
if the PA is switched off.

So to the community: who knows this, and is it desirable to
disable the TR relay if the PA is off?

Christoph,

> Am 10.02.2026 um 20:04 schrieb Luc <luc.l...@gmail.com>:
>
> Tks Christof, danke christof
>
> I dont have 5wtt on the main "ant" connector if i disable the pa..so far so good...
> Habe keine 5 wtt auf antenna connector wen ich die pa abschalte(disabel )
>
> if i read everything correctly it must be giving low power on the rf1 connector is duplex enabled...correct me if i'm wrong...
> wenn ich alles gut gelesen habe dann muss es low power geben am rf1 connector wen pa is abgeschaltet un duplex is "on"
>
> so the software is Thetis -Hl2 last version...und Hw is the Hermes lite2👍😉
>

[John Williams]

I have used RF1 in the past to excite a buffer amplifier for my Am transmitter. All I ever had to do on Thetis is disable the PA. I had to provide t/r switching in my buffer amp and also made an option to select a receive only beverage antenna.
Sent from my iPhone

> On Feb 11, 2026, at 4:40 AM, Christoph v. Wüllen <DL1...@darc.de> wrote:
>
> According to the HL2 schematic, there is a relais U10/U11 which routes the RF output

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[Hamish Kellock]

Hi Christoph,

I am using the RF1 (lo power Tx) and RF3 (Rx) interfaces for full duplex and half duplex connections to various transverters. I have physically disabled the PA stage by removing the PA output transformer, and disabled the use of the PA in either piHPSDR or Quisk software. I use the EXTTR output to indicate to my external controller the transmit output state. I can say that RF1 gets the output under these circumstances with the current SW of these two applications.

Hamish, OH2GAQ

Hamish Kellock

["Christoph v. Wüllen"]

If you use RF3 instead of the antenna jack then of course the T/R relay is of no concern for you.
The question was, if one uses the main ant jack for RX, how to disable the T/R relay.
I *think*

Vbias is disabled if ADDR=0x09,bit=19 is set to zero

T/R relay sticks in "RX" position if ADDR=0x09,bit19 is
set to zero AND ADDR=0x09,bit18 iset set to 1

but it would be interesting to me to hear a confirmation of that.
I have made a change to piHPSDR such that

PA enabled: bit19=1 and bit18=0
PA disabled: bit19=0 and bit18=1

(bit18 used to be 0 all the time up to now)

and I wonder if this is the way to go.

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[John Williams]

My hermes lite only has RF1 and antenna. I use RF1 to feed the amp input directly, not switched. I switch ANT between regular antenna or receive only antenna. When the HL2 goes into transmit, I use exttr to switch the input to the HL2 ant port to ground to null out any signal that may be induced on the line from my big transmitter feeding back into the HL2. I assumed that since the unit is in full duplex, I can and do see a TX waveform on the panadapter even if ANT is grounded, very low level. I use it to monitor my modulation and bandwidth of the signal. Since the PA is off, there should be negligible output power on that ANT port, even if the TR relay is being activated, correct? I never looked for any present, though. 

Do you think that during TX with the relay still being activated, that the port sees the same output as RF1? I assumed it saw nothing. 

---

From: herme...@googlegroups.com <herme...@googlegroups.com> on behalf of "Christoph v. Wüllen" <DL1...@darc.de>
Sent: Wednesday, February 11, 2026 7:49 AM
To: hamish....@pp.inet.fi <hamish....@pp.inet.fi>
Cc: herme...@googlegroups.com <herme...@googlegroups.com>
Subject: Re: rf1-ant power

 

To view this discussion visit https://groups.google.com/d/msgid/hermes-lite/BCF5A5E1-8E9C-40D3-96B0-4E0E636286D1%40darc.de.

["Christoph v. Wüllen"]

Hmm... if you ground your ant input during transmit and the HL2 TR relay is in "TX" position,
the RF front end is open (not grounded!) so it can pick up from "anywhere".

> Am 11.02.2026 um 15:11 schrieb John Williams <jswi...@gmail.com>:
>
> My hermes lite only has RF1 and antenna. I use RF1 to feed the amp input directly, not switched. I switch ANT between regular antenna or receive only antenna. When the HL2 goes into transmit, I use exttr to switch the input to the HL2 ant port to ground to null out any signal that may be induced on the line from my big transmitter feeding back into the HL2. I assumed that since the unit is in full duplex, I can and do see a TX waveform on the panadapter even if ANT is grounded, very low level. I use it to monitor my modulation and bandwidth of the signal. Since the PA is off, there should be negligible output power on that ANT port, even if the TR relay is being activated, correct? I never looked for any present, though.
>

> Do you think that during TX with the relay still being activated, that the port sees the same output as RF1? I assumed it saw nothing. From: herme...@googlegroups.com <herme...@googlegroups.com> on behalf of "Christoph v. Wüllen" <DL1...@darc.de>

[John Williams]

Yes, you are correct. I will need to recheck this out. I was assuming in my design that disabling the PA also disabled the relay. My transmitter is down right now due to having to move it. I will however test the HL2 to see if the relay is moving with PA off. I suspect you are correct and it is still functioning. 

---

From: "Christoph v. Wüllen" <DL1...@darc.de>
Sent: Wednesday, February 11, 2026 10:07 AM
To: John Williams <jswi...@gmail.com>

[John Williams]

Reading the schematic, a pair of PE4259s control whether RF1 is active or if the power is fed to the input of the PA. TR relay is controlled by INTTR. So, when the PA is disabled, no power is sent to the PA, only sent to RF1. Unless the gateware is otherwise shutting off INTTR, it would be likely to be cycling. Also note, that if INTTR is being disabled the N2ADR RX HPF may also be likewise disabled as it is controlled by INTTR.

---

From: John Williams <jswi...@gmail.com>
Sent: Wednesday, February 11, 2026 10:13 AM
To: "Christoph v. Wüllen" <DL1...@darc.de>