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Hi,

I’m new to the community! I’m wondering why there isn’t a way to add in mice low end on FM and why it cannot be allowed to be passed through while on semplix mode?

I would like to see an option where you’re allowed to do that to allow those nice Low end frequencies through that I know pass through on AM/ SSB.

THANKS!
Dan
W7ZAR

Simplex

Interesting question. This would be on 10M FM, right? I wonder how many radios allow for the CTCSS receive filter, which cuts off at 300Hz, to be disabled? Thetis allows that on receive (in Setup > DSP > FM), do any other radios?

Assuming that TX CTCSS is disabled in Thetis, are you certain it is filtering TX audio at 300Hz? Have you listened on a radio that is known to be able to receive below 300Hz? I've never tried this myself and I'm not sure I do have a way to try it here.

Self monitoring on FM is almost impossible due to the effect that desense has. I tried messing with wide band FM audio quality years back and unless you modify a receiver, most have the high pass filtering for the PL range.

I basically just let it go with basic audio cleanup and left it alone.

What I didn’t try was recording from the audio output of a second receiver and that would work much better if you could move the receiver out of the near RF field.

When I want to hear how I sound I tap into the antenna output with an RF sampler and feed that into an SDR dongle running in Simon Brown's SDR Console and record the audio then play it back.

Mark

w-u-2-o wrote:Simplex

Interesting question. This would be on 10M FM, right? I wonder how many radios allow for the CTCSS receive filter, which cuts off at 300Hz, to be disabled? Thetis allows that on receive (in Setup > DSP > FM), do any other radios?

Assuming that TX CTCSS is disabled in Thetis, are you certain it is filtering TX audio at 300Hz? Have you listened on a radio that is known to be able to receive below 300Hz? I've never tried this myself and I'm not sure I do have a way to try it here.

Yep, I’ve tried! And it still sucks on the audio! On RX and TX

kc2rgw wrote:Self monitoring on FM is almost impossible due to the effect that desense has. I tried messing with wide band FM audio quality years back and unless you modify a receiver, most have the high pass filtering for the PL range.

I basically just let it go with basic audio cleanup and left it alone.

What I didn’t try was recording from the audio output of a second receiver and that would work much better if you could move the receiver out of the near RF field.

I recorded it on thetis but it still sounds pinched off no HIFI sound like on AM and SSB

I have confirmed that the limiting factor is the TX pre-emphasis filter, which is set to 300-3000Hz as per the de facto industry standard.

Question for @W7ZAR -- how many people do you think would benefit from making a change to this? How many communications radios have the capability to extend the receive passband below 300Hz when in FM mode?

I'm certain the ICOM ID-5100 will receive audio below 300 Hz, I have mine running the receive audio thru VM Potato and I have to add a low-cut filter to get rid of the 110.9 CTCSS tone everyone in our local simplex group employs to block out a local quarmer.

I don't hear the tone when listening on the 5100's tiny built-in speaker but I hear it when listening thru the rear audio output jack.

Mark

Edit: Corrected model to ID-5100

w-u-2-o wrote:Question for @W7ZAR -- how many people do you think would benefit from making a change to this? How many communications radios have the capability to extend the receive passband below 300Hz when in FM mode?

honestly not many radios even the Apache radios.