Kenwood R2000 + Transmitter - UK Vintage Radio Repair and Restoration Discussion Forum

Alf · 13th Oct 2012, 10:17 pm

I've recently acquired a Kenwood R2000 receiver, hopefully, I'd like to use it with small QRP transmitters, say around 10W or less. Would I need to use any special precautions to protect the front end of this receiver? From the circuit diagram, there appears to be a zener diode from the aerial to chassis.

Aub · 13th Oct 2012, 11:35 pm

Hi Alf,

I wouldn't think you'd have any trouble from 10 watts or less. I sometimes use a small transistorised receiver, instead of my AR88, and that's been ok when I fire up my 50 watt homebrew rig.

73's ( for those who don't know, that means best wishes )

Aub, G4KQL

Radio Wrangler · 14th Oct 2012, 9:03 am

I use a 2-pole changeover toggle switch with one pole switching the antenna, the other muting whatever RX I'm using (EA12, RA1792, ICOM R9000)

You don't just want to avoid damage to the RX, you also don't want to waste TX power. A third thing is that a heavily overloaded receiver, when you have slow AGC selected for CW or SSB can take too long to get back to normal sensitivity and you lose words on every over.

David GM4ZNX

Alf · 14th Oct 2012, 4:28 pm

Thanks, I managed to get hold of the manual earlier today, it seems like it's not necessary to do anything.

majoconz · 15th Oct 2012, 9:17 pm

Probably not necessary to protect the R2000 (I have one that I bought in 1982 or so - still goes well!) but how do you propose killing the noise/feedback if you are using simplex - and the desensitising? I would be inclined to short the antenna to ground via the PTT line and maybe a relay - but then the front end noise will rise.

Are you troubled with background noise with no signal - I have done a mod which replaces the tone control with a RF gain pot which works very well - I always had the tone control turned up to max anyway.

Alf · 15th Oct 2012, 10:44 pm

Hello Martin, I'm not exactly sure that I follow you about the noise/feedback. According to the manual, there's a pin on the "remote" that can be grounded, this mutes the R2000 on transmit, I could do this with a spare connection on the tx/rx relay.

No problem with background noise at the moment, but I'd like details of the mod for future use. The receiver is 20 years old and in showroom condition, it's surprising what turns up on freecycle.

majoconz · 16th Oct 2012, 12:31 am

I'd forgotten about the remote connector, but now I remember that I had used it with a Yaesu FT901 a long time ago that also had a terminal that came off the back contact of the antenna changeover relay so that you could run a second receiver - handy for spotting up and down the band without disturbing the Tx frequency - but the 901 receiver was much hotter then the 2000!

If you PM me your email address I'll send you the circuit for the RF gain pot mod - it need a bit of dismantling and there is only the circuit - no explanation. I just remove the tone capacitor and used the vacant PC board hole for the new wire.

majoconz · 16th Oct 2012, 4:04 am

Sorry, I didn't answer your question. I meant that if you have the R2000 running through a speaker and turned up so that you hear the other guy, then if you then transmit through an open mike then the receiver audio will feedback or at least make some strange noise.

That's why I like using a headset and boom microphone - complete control over received audio and you get that little bit of sidetone for reassurance.

13th Oct 2012, 10:17 pm	#1
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Kenwood R2000 + Transmitter I've recently acquired a Kenwood R2000 receiver, hopefully, I'd like to use it with small QRP transmitters, say around 10W or less. Would I need to use any special precautions to protect the front end of this receiver? From the circuit diagram, there appears to be a zener diode from the aerial to chassis.

13th Oct 2012, 11:35 pm	#2
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,039	Re: Kenwood R2000 + Transmitter Hi Alf, I wouldn't think you'd have any trouble from 10 watts or less. I sometimes use a small transistorised receiver, instead of my AR88, and that's been ok when I fire up my 50 watt homebrew rig. 73's ( for those who don't know, that means best wishes ) Aub, G4KQL __________________ Life's a long song, but the tune ends too soon for us all.

14th Oct 2012, 9:03 am	#3
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,879	Re: Kenwood R2000 + Transmitter I use a 2-pole changeover toggle switch with one pole switching the antenna, the other muting whatever RX I'm using (EA12, RA1792, ICOM R9000) You don't just want to avoid damage to the RX, you also don't want to waste TX power. A third thing is that a heavily overloaded receiver, when you have slow AGC selected for CW or SSB can take too long to get back to normal sensitivity and you lose words on every over. David GM4ZNX __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

14th Oct 2012, 4:28 pm	#4
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Re: Kenwood R2000 + Transmitter Thanks, I managed to get hold of the manual earlier today, it seems like it's not necessary to do anything.

15th Oct 2012, 9:17 pm	#5
majoconz Heptode Join Date: Jan 2008 Location: Ashhurst, Manawatu, New Zealand Posts: 571	Re: Kenwood R2000 + Transmitter Probably not necessary to protect the R2000 (I have one that I bought in 1982 or so - still goes well!) but how do you propose killing the noise/feedback if you are using simplex - and the desensitising? I would be inclined to short the antenna to ground via the PTT line and maybe a relay - but then the front end noise will rise. Are you troubled with background noise with no signal - I have done a mod which replaces the tone control with a RF gain pot which works very well - I always had the tone control turned up to max anyway. __________________ Cheers - Martin ZL2MC

15th Oct 2012, 10:44 pm	#6
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Re: Kenwood R2000 + Transmitter Hello Martin, I'm not exactly sure that I follow you about the noise/feedback. According to the manual, there's a pin on the "remote" that can be grounded, this mutes the R2000 on transmit, I could do this with a spare connection on the tx/rx relay. No problem with background noise at the moment, but I'd like details of the mod for future use. The receiver is 20 years old and in showroom condition, it's surprising what turns up on freecycle.

16th Oct 2012, 12:31 am	#7
majoconz Heptode Join Date: Jan 2008 Location: Ashhurst, Manawatu, New Zealand Posts: 571	Re: Kenwood R2000 + Transmitter I'd forgotten about the remote connector, but now I remember that I had used it with a Yaesu FT901 a long time ago that also had a terminal that came off the back contact of the antenna changeover relay so that you could run a second receiver - handy for spotting up and down the band without disturbing the Tx frequency - but the 901 receiver was much hotter then the 2000! If you PM me your email address I'll send you the circuit for the RF gain pot mod - it need a bit of dismantling and there is only the circuit - no explanation. I just remove the tone capacitor and used the vacant PC board hole for the new wire. __________________ Cheers - Martin ZL2MC

16th Oct 2012, 4:04 am	#8
majoconz Heptode Join Date: Jan 2008 Location: Ashhurst, Manawatu, New Zealand Posts: 571	Re: Kenwood R2000 + Transmitter Sorry, I didn't answer your question. I meant that if you have the R2000 running through a speaker and turned up so that you hear the other guy, then if you then transmit through an open mike then the receiver audio will feedback or at least make some strange noise. That's why I like using a headset and boom microphone - complete control over received audio and you get that little bit of sidetone for reassurance. __________________ Cheers - Martin ZL2MC