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Greetings!

I SECOND the notion that anyone reading this - should ALSO READ THROUGH THIS THREAD TOO...

https://www.worldwidedx.com/threads/2sc2999-mod-analysis.161809/

I HIGHLY RECOMMEND READING BOTH OF THESE THREADS BEFORE ATTEMPTING THIS MODIFICATION...

Continuing on...

In review, this mod for the Cobra 29 should be the easier radio to do it on, for the effort of "drop in" is easier than say a RCI 696 that being SMD...

Unit 399 raised some pointers that the rest of us need to HEED...

GAIN of Part Hfe (being Frequency Of Interest)
BIAS of Part at expected Hfe (hey the things gotta use Power)
DIODES as part of the RX process...(Germanium Geraniums versus Schottky)
any required improvements to the chassis BIAS of AGC, ANL work, and performance tuning of Noise Blanker...When I mention AGC, something as simple as R31 and R35 as well as tweaks to C30/C31 can change performance...

To help some of those that are technically curious about this thread...
[ATTACH=full]23461[/ATTACH]

The above is important, for a "drop in" is considered an immediate FAIL because no ideal bias adjustments were done - for the part to show improvement, the circuit needs to be idealized for the new part to even function in a capacity we are expecting else no sense in buying a Ferrari that uses gas, when all you've got is diesel fuel available to use...You may be able to get it to run but not very well.

Then there is the opposite, dropping in this part may make it perform and show work within specs of the OEM part. Then all we've proven is that the part simply can REPLACE that part - not offer any improvement in drive or Signal To Noise.

We also have a Carborundrum:
Although we have tried, there are some that make the comments about the replacement of Schottky and or Germanium that if they are old or have failed it is best to replace them - good advice.

Does little though to help us understand the noise we hear in a receive even with no antenna attached - again the effort to replace them and what they can do to the radios' "Noise floor" is it more of a gain factor?. Using the word "gain" without clarification many would assume the parts involved would be the problem. Not always, for many instances there is a feedback principle being applied, regarding AGC reaction using the Divider network resistor R31 and R35 (Cobra 29).

The AGC relies on the negative going aspect of power, as detected carrier + Audio Signal, detected from the 2nd IF output and is used a means to reduce power when the received amplified signal is strong enough in signal strength it can damage parts within the RF amp strip - and this means of Negative Feedback to reduce distortion artifacts from excessive signal drive and overload is applied to key points along the RF strips' amplifier stages - this also provides a means to control IF images that are summed into the detected signal as a signal in itself with it's own inherent RF signature including the noises produced by it as it travels the strip.

As mentioned earlier -
If allowed to "tweak" AGC levels, as well as apply optimum BIAS drive levels to the devices we wish to test, using them in a close as possible signature of the original RADIO OEM design networks (Read: radios itself not test circuit) - the devices then can be allowed to run their full drive range and , showing power curve results. At least with the effort of adjusting AGC - we learn from the application which devices perform the best under which condition working with and against the noises we are try to remove.

And in reciprocal - even the support parts replacing other portions of the RX strip the original OEM may affect Receiver performance and obtain the desired results without having the NEED to install the part we wanted to drop in in the first place.

EXAMPLE:
The 2SC1674 (to Be Fair)
[ATTACH=full]23457[/ATTACH]

Compare this test circuit when you evaluate the Noise and Hfe figures

So we'd better keep our ducks in a row and look ahead...because what some may call a better result - some would call a performance hit...

.. Will add more as time permits...

...Stay tuned...
Regards!
:+> Andy <+:

<blockquote data-quote="Handy Andy" data-source="post: 624300" data-attributes="member: 52309">Greetings!I SECOND the notion that anyone reading this - should ALSO READ THROUGH THIS THREAD TOO...<a href="https://www.worldwidedx.com/threads/2sc2999-mod-analysis.161809/" target="_blank">https://www.worldwidedx.com/threads/2sc2999-mod-analysis.161809/</a>I HIGHLY RECOMMEND READING BOTH OF THESE THREADS BEFORE ATTEMPTING THIS MODIFICATION...Continuing on...In review, this mod for the Cobra 29 should be the easier radio to do it on, for the effort of &quot;drop in&quot; is easier than say a RCI 696 that being SMD...Unit 399 raised some pointers that the rest of us need to HEED...GAIN of Part Hfe (being Frequency Of Interest)BIAS of Part at expected Hfe (hey the things gotta use Power)DIODES as part of the RX process...(Germanium Geraniums versus Schottky)any required improvements to the chassis BIAS of AGC,&nbsp; ANL work, and performance tuning of Noise Blanker...When I mention AGC, something as simple as R31 and R35 as well as tweaks to C30/C31 can change performance...To help some of those that are technically curious about this thread...[ATTACH=full]23461[/ATTACH]The above is important, for a &quot;drop in&quot; is considered an immediate FAIL because no ideal bias adjustments were done - for the part to show improvement, the circuit needs to be idealized for the new part to even function in a capacity we are expecting else no sense in buying a Ferrari that uses gas, when all you&#039;ve got is diesel fuel available to use...You may be able to get it to run but not very well.Then there is the opposite, dropping in this part may make it perform and show work within specs of the OEM part. Then all we&#039;ve proven is that the part simply can REPLACE that part - not offer any improvement in drive or Signal To Noise.We also have a Carborundrum:Although we have tried, there are some that make the comments about the replacement of Schottky and or Germanium that if they are old or have failed it is best to replace them - good advice.Does little though to help us understand the noise we hear in a receive even with no antenna attached - again the effort to replace them and what they can do to the radios&#039; &quot;Noise floor&quot; is it more of a gain factor?. Using the word &quot;gain&quot; without clarification many would assume the parts involved would be the problem. Not always, for many instances there is a feedback principle being applied, regarding AGC reaction using the Divider network resistor R31 and R35 (Cobra 29).The AGC relies on the negative going aspect of power, as detected carrier + Audio Signal, detected from the 2nd IF output and is used a means to reduce power when the received amplified signal is strong enough in signal strength it can damage parts within the RF amp strip - and this means of Negative Feedback to reduce distortion artifacts from excessive signal drive and overload is applied to key points along the RF strips&#039; amplifier stages - this also provides a means to control IF images that are summed into the detected signal as a signal in itself with it&#039;s own inherent RF signature including the noises produced by it as it travels the strip.

As mentioned earlier - 
If allowed to &quot;tweak&quot; AGC levels, as well as apply optimum BIAS drive levels to the devices we wish to test, using them in a close as possible signature of the original RADIO OEM design networks (Read: radios itself not test circuit) - the devices then can be allowed to run their full drive range and , showing power curve results. At least with the effort of adjusting AGC - we learn from the application which devices perform the best under which condition working with and against the noises we are try to remove.
 
And in reciprocal - even the support parts replacing other portions of the RX strip the original OEM may affect Receiver performance and obtain the desired results without having the NEED to install the part we wanted to drop in in the first place.EXAMPLE:
The 2SC1674 (to Be Fair)[ATTACH=full]23457[/ATTACH]Compare this test circuit when you evaluate the Noise and Hfe figures
So we&#039;d better keep our ducks in a row and look ahead...because what some may call a better result - some would call a performance hit..... Will add more as time permits......Stay tuned...Regards!:+&gt; Andy &lt;+:</blockquote>

[QUOTE="Handy Andy, post: 624300, member: 52309"] Greetings! I SECOND the notion that anyone reading this - should ALSO READ THROUGH THIS THREAD TOO... [COLOR=rgb(0, 0, 179)][B][URL]https://www.worldwidedx.com/threads/2sc2999-mod-analysis.161809/[/URL][/B][/COLOR] [SIZE=5][COLOR=rgb(255, 0, 0)][B]I HIGHLY RECOMMEND READING BOTH OF THESE THREADS BEFORE ATTEMPTING THIS MODIFICATION...[/B][/COLOR][/SIZE] Continuing on... In review, this mod for the Cobra 29 should be the easier radio to do it on, for the effort of "drop in" is easier than say a RCI 696 that being SMD... Unit 399 raised some pointers that the rest of us need to HEED... GAIN of Part Hfe (being Frequency Of Interest) BIAS of Part at expected Hfe (hey the things gotta use Power) DIODES as part of the RX process...(Germanium Geraniums versus Schottky) any required improvements to the chassis BIAS of AGC, ANL work, and performance tuning of Noise Blanker...When I mention AGC, something as simple as R31 and R35 as well as tweaks to C30/C31 can change performance... To help some of those that are technically curious about this thread... [ATTACH=full]23461[/ATTACH] The above is important, for a "drop in" is considered an immediate FAIL because no ideal bias adjustments were done - for the part to show improvement, the circuit needs to be idealized for the new part to even function in a capacity we are expecting else no sense in buying a Ferrari that uses gas, when all you've got is diesel fuel available to use...You may be able to get it to run but not very well. Then there is the opposite, dropping in this part may make it perform and show work within specs of the OEM part. Then all we've proven is that the part simply can REPLACE that part - not offer any improvement in drive or Signal To Noise. [B][SIZE=5]We also have a Carborundrum:[/SIZE][/B] [COLOR=rgb(179, 0, 0)]Although we have tried, there are some that make the comments about the replacement of Schottky and or Germanium that if they are old or have failed it is best to replace them - good advice. [/COLOR] [COLOR=#006600]Does little though to help us understand the noise we hear in a receive even with no antenna attached - again the effort to replace them and what they can do to the radios' "Noise floor" is it more of a gain factor?. Using the word "gain" without clarification many would assume the parts involved would be the problem. Not always, for many instances there is a feedback principle being applied, regarding AGC reaction using the Divider network resistor R31 and R35 (Cobra 29).[/COLOR] [COLOR=rgb(179, 0, 0)][/COLOR] [INDENT][INDENT][COLOR=rgb(179, 0, 0)]The AGC relies on the negative going aspect of power, as detected carrier + Audio Signal, detected from the 2nd IF output and is used a means to reduce power when the received amplified signal is strong enough in signal strength it can damage parts within the RF amp strip - and this means of Negative Feedback to reduce distortion artifacts from excessive signal drive and overload is applied to key points along the RF strips' amplifier stages - this also provides a means to control IF images that are summed into the detected signal as a signal in itself with it's own inherent RF signature including the noises produced by it as it travels the strip.[/COLOR] [COLOR=rgb(0, 0, 102)][B][/B] [B]As mentioned earlier - [/B] If allowed to "tweak" AGC levels, as well as apply optimum BIAS drive levels to the devices we wish to test, using them in a close as possible signature of the original RADIO OEM design networks (Read: radios itself not test circuit) - the devices then can be allowed to run their full drive range and , showing power curve results. At least with the effort of adjusting AGC - we learn from the application which devices perform the best under which condition working with and against the noises we are try to remove. [/COLOR][/INDENT][/INDENT] And in reciprocal - even the support parts replacing other portions of the RX strip the original OEM may affect Receiver performance and obtain the desired results without having the NEED to install the part we wanted to drop in in the first place. [INDENT][B]EXAMPLE:[/B] The 2SC1674 (to Be Fair)[/INDENT] [ATTACH=full]23457[/ATTACH] [INDENT][INDENT]Compare this test circuit when you evaluate the Noise and Hfe figures[/INDENT][/INDENT] So we'd better keep our ducks in a row and look ahead...because what some may call a better result - some would call a performance hit... .. Will add more as time permits... ...Stay tuned... Regards! :+> Andy <+: [/QUOTE]

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