hpr-knowledge-base/hpr_transcripts/hpr2688.txt

Episode: 2688
Title: HPR2688: Explaining the controls on my Amateur HF Radio Part 5
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2688/hpr2688.mp3
Transcribed: 2025-10-19 07:33:51

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This in HPR episode 2688 entitled, explaining the controls on my amateur HF radio part 5 and in part of the series, HAM radio, QSK.
It is hosted by MrX and in about 17 minutes long and carrying an explicit flag.
The summary is, in this episode I cover the remaining receiver section controls on the DS914.
This episode of HBR is brought to you by an honesthost.com.
Get 15% discount on all shared hosting with the offer code HBR15. That's HBR15.
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Hello and welcome hacker public radio audience.
Welcome to this podcast. As usual I'd like to thank the people at HBR for making this service
available to us all. It's truly an invaluable service that they provide. I've got a lot of
effort to streamline it and make it as easy as possible for you to contribute. HBR is a community
led podcast provided by the community for the community. That means you can contribute to.
Why don't you give it a go. This is the final part of my series on the controls of my
KMU TS940S HF at high frequency amateur radio. You'll be sick of the thing. It covers the
remaining receiver section of the receiver controls in the receiver section of the radio
covers AFRF gain, CW variable bandwidth tuning, SSB slope tuning and I mentioned some of the pros
and cons of the end up, mentioned some of the pros and cons of owning such a radio.
Anyway hope you enjoy it so sit back and enjoy.
Okay so we left off for the RIT slash XIT control. The next control along is a dual
control with tube. Let's control along is a dual function control, dual function, lottery control,
AF gain and RF gain, sorry AF and RF is what's marked above it and this I'll just turn a radio on.
And the inner one is AF which stands for audio frequency and the outer one is RF which is
radio frequency. So if you turn the AF one up it's just the volume. I mean there you go so
that's it turning the volume up but they call it AF audio frequency. Just again in the audio frequency
stages of the radio. The RF one what happens there is it's if any if you have them
had a other CB radio or something like that or another receiver what generally happens is
you know you've got your RF gain you turn it down and the signal drops.
But this radio doesn't do that what happens is you turn the RF gain down and the signal gets weaker
but let's go through that again. This radio doesn't do that what happens is if I go with a blank
bit a quite piece of the radio spectrum and of course I can't actually find a bit because there's
so much noise going on but just now but say the background noise was the signal strength was
sitting at 2 so in other words you know there's just nothing to the hiss and the signal meter is
wavering about the number 2. The conventional RF gain if you turn it down and that would go even
lower and disappear but what happens with this radio is the signal meter starts to climb up.
So what is doing is it's it's it's known as raising the noise floor so you know you've got
a signal and the dynamic range of the radio is between the stronger signal can hear and the
weaker signal and when you turn the RF gain the noise floor rises to meet the signal that you're
receiving. So the beauty of that is that your signal strength remains the same so if I'm listening
to a radio station and it's a bit strong I can just turn the RF gain back and the noise floor
comes up to meet the signal but you still get the same signal strength on the on the meter until
eventually disappear of course but it's still a lot of fun to disappear at which point where they
the noise floor reaches the same strength as as a signal and then you don't hear anything.
So if I just go to or try and get a bit more scored for example if we can
well there's a there's a tone for example and if I let's just do the notch again because that's
for letting you hear how well the notch works. So there you go there's a notch filter and in
I take it out. Oh the tone stopped. Flaming typical. That was a perfect tone for that too.
There you go. Morse code. Come on Morse. Come back, notch, disappear, notch.
So you can hear that that notch filter works really well but anyway if I got a signal and I'll
use the RF gain again so that's what we're really talking about.
Can't find one. Right. We're turning the RF gain. That's synch is about
plus 20 dB something like that and of course he stopped speaking of course. Dad is a K
which not stopped speaking so hopefully we go. Now I'm going to turn the gain up.
There I've gain up or down I should say and now you can't hear it but
but the meter hasn't gone down so it's a bit of a strange way of thinking about but it's
it's quite a clever idea really rather than just just dropping the signal strength.
A subtle difference to the way the RF control works. I'm seeing it on a typical CBA or whatever
but there you go. So that's AF gain and RF gain. I bet that's confused the heck out of you.
This is like an off the cuff thing and I've not prepared any notes or anything like that and
I do apologise. So we go to the last two controls on the bottom right hand corner of the rail.
The left hand one is CWVBT and that's CW which stands for Carrier Wave as more
code VBT variable bandwidth something but it's essentially allows you to
the radio becomes super super selective very very thin and narrow too narrow for voice but allows
you to really separate if you've got two more stations running very close to one another you can
select just one with careful adjustment tuning affect if you're a keen morse operator a morse
signal will get through where an audio voice signal won't you know if you're a really really
weak signal a morse signal a punch through and if you've got a lot interference and noise and
whatnot on the band other morse stations coming in and out then this filter clears all that up
or can do it's actually very good and you get the variable BBT you get a graphic representation
on the sub display the lines converged depending on how narrow the the the width of the lines because
there's a series of of vertical bars printed in the sub control sub
menu sub panel display and as you turn the VBT it kind of clicks
and when you do that the the number of vertical bars decreases and increases to to um
graphically simulate the width of the the the the filter the width of the receiver basically
so I see I can get this to work as well so we've had a long time since I've done it
there's a no morse cause a bit quite just now I better go into CW mode actually CW mode
and I can't find any more sks typical maybe just to take my word for it um it works really well
I don't know what I think I'm sure nowadays I've got modern news I've got digital signal processors
which can do this sort of thing no I can't find any more the world salt has appeared um so
I just take my word for it and it would probably be complicated to set up anyway and the finally
um oh there's some more scoring now no I mean uh finally the the bottom uh right hand
control the the very bottom uh right hand corner it says SSB slope tune and there's an
inner ring and outer ring dual control again the inner one has a high against it and outer one has a
low and what this seems to do is it um it's like a high pass filter and low pass and low pass audio
filter so that if you've got a lot of noise in the band predominantly low frequency noise you can
you can reduce it by um turning the is it a low pass one up for example uh
so actually turning that down let's let's cut any high frequency sound so you let the low
through basically let's even get a voice signal so you can hear how it sounds
if I can find any voice that is
oh
lock going on near
now there that sounds as you how it's just almost distorted but if I turn the
all right
now
there's high frequency
right that that station calling there's a very low frequency signal so I could I could reduce
the low frequency signal by by turning let's see if I can do this
yeah
yeah turning the low frequency um knob up so the time that cuts the low frequency out so
there you go makes it sound more tinny
there you go so it's now a lot tinnyer but it's cut out all that noise that was coming in from the
underneath at the base um say much quieter how much cleaner it sounds now
but it affects the audio quality and like wedged if there's a lot of high frequency noise
on the band then I could cut that so
it's it's it's it's it's that noise again
yeah so it's it's a it's a basic filtering sort of basic audio filtering I guess it's about
like having an audio frequency equal a graphic equalizer where you cut the high frequency
components in no audio or the low frequency components just by turning those two knobs
basically that's what it's doing so it's as simple as that there's a whole slew of controls
um on the uh sliding top panel thing which I'm not going to bother going into this no point
uh these are kind of specials to this radio and uh for adjusting the
nope I'm not going to say any more about that it's just on your point um you wouldn't come
of course you sort of think it's a typical radio and there's also a whole slew of um
connected some plugs in the back of the radio as well which I won't cover either
I think that's probably enough you'll be sick to death at the kind with TS940S
I however love it it's a lovely radio if you get the chance of buying one um
I'm not sure they don't recommend you buy these sort of things you know I were reading um about
that and I said that you're better off buying a modern radio because uh with an old radio
signal car the chances are it'll fail now it may well be the case it'll fail and at some point um
but uh it's just a real joy to operate the controls are lovely and weighted and smooth
and uh although there's a lot of controls on it there's easy to access every single function
that happened to diving to menus of the Wii um small display um it's just a a real joy to
operate um and I'd be very sad if it if struck when it fails um and I guess we just need to buy one
these modern type radios um so there you go I say modern but it's it's I say old but I mean
although this video is old it's removed from the 1980s or whatever it's it's um it's got PLL
phase lock loop synthesis and whatnot so it's it's very very stable it doesn't it doesn't
drift around like like the old valve radios do used to do um um so it's it's very nice indeed
I'd recommend one uh if you prefer to take the risk that it doesn't break down of course
because trying to get it repaired would be very costly I would think um had a dry joint appear in it
shortly after I got it and I had to take uh take all the bits and take all the boards out and uh
it's probably the most complex thing I've ever taken to bits in my life so I would not like to uh
have to repeat that anyway I think that's enough uh of the Kenwood TS940s um thanks very much for
listening um I don't know if I haven't bored you too much this time um so if you want to contact me
I could be contacted at mrx at hpr at googlemail.com that's mrx80hpr the at symbol googlemail.com
so until next time thank you and goodbye
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