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Low RX Audio #ubitx

 

Hi!!!?

My ubitx rx audio level on 80m and 40m bands is good, but 20m and above is very low. I verified my antena with other radios and is working fine. Even the tx on 20m up to 10m is up to spec, but the receive audio is vey weak. ?Any ideas where to check??? Thanks and 73 de WP3DN
 

Do you use Farhan's ubitx v3 board or made one for yourself?


Regards
MVS Sarma
?

On Mon, Jun 18, 2018 at 9:28 AM, <3voltios@...> wrote:
Hi!!!?

My ubitx rx audio level on 80m and 40m bands is good, but 20m and above is very low. I verified my antena with other radios and is working fine. Even the tx on 20m up to 10m is up to spec, but the receive audio is vey weak.? Any ideas where to check??? Thanks and 73 de WP3DN


 

In TX how much power do you get?


Il 18/giu/2018 06:51, "Mvs Sarma" <mvssarma@...> ha scritto:
Do you use Farhan's ubitx v3 board or made one for yourself?


Regards
MVS Sarma
?

On Mon, Jun 18, 2018 at 9:28 AM, <3voltios@...> wrote:
Hi!!!?

My ubitx rx audio level on 80m and 40m bands is good, but 20m and above is very low. I verified my antena with other radios and is working fine. Even the tx on 20m up to 10m is up to spec, but the receive audio is vey weak.? Any ideas where to check??? Thanks and 73 de WP3DN



 

iz oos,
The Tx power and Rx sensitivity are different issues, I suppose.
at times if we carefully tweak the coils(LPF before 1st mixer) , in effect slight changes in their inductance vales, we can perhaps improve on sensitivity. This action? could be either increase , or decrease slightly. One has to be cautious while doing not to break the coils at the soldering point.


Regards
MVS Sarma
?

On Mon, Jun 18, 2018 at 11:34 AM, iz oos <and2oosiz2@...> wrote:

In TX how much power do you get?


Il 18/giu/2018 06:51, "Mvs Sarma" <mvssarma@...> ha scritto:
Do you use Farhan's ubitx v3 board or made one for yourself?


Regards
MVS Sarma
?

On Mon, Jun 18, 2018 at 9:28 AM, <3voltios@...> wrote:
Hi!!!?

My ubitx rx audio level on 80m and 40m bands is good, but 20m and above is very low. I verified my antena with other radios and is working fine. Even the tx on 20m up to 10m is up to spec, but the receive audio is vey weak.? Any ideas where to check??? Thanks and 73 de WP3DN




 

Most of circuitry is used for both TX and RX, so that is why I asked for TX power output. If TX works, than I would look to those parts not used on TX. Maybe there is some switch (diode or relay) that does not work properly. Maybe in this case kits like signal tracer by Hendricks may be useful to detect the defective part, solder joint, if any.


Il 18/giu/2018 08:29, "Mvs Sarma" <mvssarma@...> ha scritto:
iz oos,
The Tx power and Rx sensitivity are different issues, I suppose.
at times if we carefully tweak the coils(LPF before 1st mixer) , in effect slight changes in their inductance vales, we can perhaps improve on sensitivity. This action? could be either increase , or decrease slightly. One has to be cautious while doing not to break the coils at the soldering point.


Regards
MVS Sarma
?

On Mon, Jun 18, 2018 at 11:34 AM, iz oos <and2oosiz2@...> wrote:

In TX how much power do you get?


Il 18/giu/2018 06:51, "Mvs Sarma" <mvssarma@...> ha scritto:
Do you use Farhan's ubitx v3 board or made one for yourself?


Regards
MVS Sarma
?

On Mon, Jun 18, 2018 at 9:28 AM, <3voltios@...> wrote:
Hi!!!?

My ubitx rx audio level on 80m and 40m bands is good, but 20m and above is very low. I verified my antena with other radios and is working fine. Even the tx on 20m up to 10m is up to spec, but the receive audio is vey weak.? Any ideas where to check??? Thanks and 73 de WP3DN




 

It is a V3 ubitx board. I'm using CEC firmware. I get about 10w on 20m and 5w on 10m.?
 

Thats good, what is your antenna ?

Raj

At 18/06/2018, you wrote:
It is a V3 ubitx board. I'm using CEC firmware. I get about 10w on 20m and 5w on 10m.
 

It is just a dipole with 300ohm line. Also use a CHA 250 b.?
 

If in doubt whether it is fine or not you might think to build a small signal generator that is able to generate just an above noise level S3 and and a good S9 signal. I made the using the manual and assembled it on copper board. I find it very useful to check the sensitivity of any receiver. You can add crystals or use the same crystal at the armonics (eg.? a 14mhz crystal may be used for 28mhz albeit is something like 10db attenuated).


Il 18/giu/2018 16:32, <3voltios@...> ha scritto:
It is just a dipole with 300ohm line. Also use a CHA 250 b.?

 

Have a usb oscilloscope with built in dds. Will check today. Thanks for the idea.
 

Ok. Using the output of a dds generator and different attenuator blocks, to get the same audio out at 10m had to reduce att by 20db compared to 40m.

So what section should I start looking for the difference??
 

Check the obvious first. From the antenna input to the audio. So check first the stage from the antenna connector to the lowpass filter.


Il 19/giu/2018 05:32, "El Calvo" <3voltios@...> ha scritto:

Ok. Using the output of a dds generator and different attenuator blocks, to get the same audio out at 10m had to reduce att by 20db compared to 40m.

So what section should I start looking for the difference??

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