Re: [baofeng_uv5r] C76 = 15pF - need removal


Sep 7

 


----------------------------

#58705 Sep 7

Hi guys,



Need to identify on all Baofeng boards (and remove) the C76 from UHF input frontend filter

as it is a DIRECT RF path from antenna to the UHF RX wideband input amplifier transistor Q10 ...

Through this capacitor strong local UHF signals bypass normal RF filtering path and saturate the receiver input on UHF band ...

This explains "intermodulations" that most of the people experience on the UHF band ...



Best regards,

Silviu



----------------------------

#58707 Sep 7

Mine is pretty deaf on VHF but works great on UHF.



From: "Silviu Isari silviuisari@... [baofeng_uv5r]" baofeng_uv5r@yahoogroups.com>

Hi guys,



Need to identify on all Baofeng boards (and remove) the C76 from UHF input frontend filter

as it is a DIRECT�� RF path from antenna to the UHF RX wideband input amplifier transistor Q10 ...

Through this capacitor strong local UHF signals bypass normal RF filtering path and saturate the receiver input on UHF band ...

This explains "intermodulations" that most of the people experience on the UHF band ...



----------------------------

#58708 Sep 7

Hi Scott,



Are you using the supplied stock antenna ? Do you test in a urban building area ?



Silviu - 73 de YO9RVE



--------------- On Thu, 9/7/17, 'Scott, KB3JQQ' kb3jqq@... [baofeng_uv5r] baofeng_uv5r@yahoogroups.com> wrote:

Mine is pretty deaf on VHF but works great on UHF.



----------------------------

#58709 Sep 7

Stock rubber resistor.

I am 2 miles away from 2 radio stations and a 1000 watt weather site.

I need to use an Icom here at a minimum.



From: "Silviu Isari silviuisari@... [baofeng_uv5r]" baofeng_uv5r@yahoogroups.com>

Hi Scott,



Are you using the supplied stock antenna ? Do you test in a urban building area ?



Silviu - 73 de YO9RVE



----------------------------

#58710 Sep 7

Oh that explains the VHF "silence" of the Baofeng ...:)

Actually with some Baofengs I was able to open very very remote VHF repeaters (like 100 .. 200km away)

when VHF band is all clean (at night or in the morning etc.)

Once some strong local signal starts ...the VHF receiver becomes deaf ...

I guess the AGC inside RDA1846 is doing this ...



73 de YO9RVE

--------------- On Thu, 9/7/17, 'Scott, KB3JQQ' kb3jqq@... [baofeng_uv5r] baofeng_uv5r@yahoogroups.com> wrote:



Stock rubber resistor.

I am 2 miles away from 2 radio stations and a 1000 watt weather site.

I need to use an Icom here at a minimum.



----------------------------

#58711 Sep 7

It's a $30.throw away radio. Why modify junk? Buy quality instead.

On Sep 7, 2017 9:51 AM, "Silviu Isari silviuisari@... [baofeng_uv5r]" baofeng_uv5r@yahoogroups.com> wrote:

.Hi guys,



Need to identify on all Baofeng boards (and remove) the C76 from UHF input frontend filter

as it is a DIRECT RF path from antenna to the UHF RX wideband input amplifier transistor Q10 ...

Through this capacitor strong local UHF signals bypass normal RF filtering path and saturate the receiver input on UHF band ...

This explains "intermodulations" that most of the people experience on the UHF band ...



Best regards,

Silviu



----------------------------

#58713 Sep 7

have you seen what passes for "quality" these days? Even the big three radio brands (Icomm, Kenwood and Yeasue) get most of their boards manufactured by the very same companies that bring you that $30 radio (AKA the Bao Feng). Sometimes, brand name isn't any better than cheap.

DE n7zzt Eric

On Sep 7, 2017, at 8:42 AM, 'Mike W.' mewolak@... [baofeng_uv5r] wrote:

��

It's a $30��throw away radio. Why modify junk? Buy quality instead.

On Sep 7, 2017 9:51 AM, "Silviu Isari silviuisari@... [baofeng_uv5r]" baofeng_uv5r@yahoogroups.com> wrote:

��Hi guys,



Need to identify on all Baofeng boards (and remove) the C76 from UHF input frontend filter

as it is a DIRECT RF path from antenna to the UHF RX wideband input amplifier transistor Q10 ...

Through this capacitor strong local UHF signals bypass normal RF filtering path and saturate the receiver input on UHF band ...

This explains "intermodulations" that most of the people experience on the UHF band ...



Best regards,

Silviu



----------------------------

#58714 Sep 7

Awesome Work



----------------------------

#58826 Oct 5

Hello Silviu.

Please expand on "remove" C76.

If that capacitor is removed what do you suggest in order to maintain a connection between antenna and Q10? A filter?



----------------------------

#58828 Oct 5

Hi,



There is already an existing UHF band pass filter in place made of L21, L20, L19, L18 + C51, C50 ...C43 used for UHF TX path !



UHF filtered RX signals should pass to Q10 ONLY via C42 ...as I see in schematics C42 = NOP !?

Is C42 really placed on the board of any Baofeng or just ..empty placeholder ?

Seeems that nobody has got a PCB placement file on internet up to present ...



Best regards,

Silviu

--------------- On Thu, 10/5/17, theminde@... [baofeng_uv5r] baofeng_uv5r@yahoogroups.com> wrote:



Subject: Re: [baofeng_uv5r] C76 = 15pF - need removal

To: baofeng_uv5r@yahoogroups.com

Date: Thursday, October 5, 2017, 1:20 PM





.



















Hello Silviu.



Please expand on "remove" C76.



If that capacitor is removed

what do you suggest in order to maintain a connection

between antenna and Q10? A filter?



















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