The absence of a low pass filter on the input stage of a linear amplifier
doesn't always mean that you will automatically have unacceptable harmonics.
Radio amateurs have use linear amplifiers for years with a 50 ohm or 200 ohm
swamping resistor on the input at the cathode of the amplifier whether then a
low pass tuned filter.
You may very well be right there, depending on the design of the amplifier. I
have not looked at the circuit all taken a measurements.
Best regards - Bry Carling
> On Feb 13, 2014, at 9:44 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net> wrote:
>
> The filter is a Low Pass filter with a nominal cut-off at about 23 MHz or
> slightly above 15M. As designed this prevents operation above this frequency
> being on the 12/10M bands. This filter also provides attenuation of
> harmonics above the designed cut-off frequency. Now with the 12/10M filter
> installed the cut-off is raised to about 32 MHz thus allowing operation on
> 12/10M and yet still providing adequate attenuation of harmonics above that
> frequency.
>
> Removing the filter and replacing it with a jumper will allow the amp to work
> on 12/10M but WILL NOT provide ANY harmonic attenuation. Any harmonics,
> i.e. 2nd, 3rd, 4th, could fall into one of the Public Service bands. Should
> interference occur and the user complain to the FCC, a written explanation by
> the operator will be required. Frankly, in this case, I can't think of an
> explanation that would be acceptable. Just remember, it is your amp and your
> license.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message ----- From: <w8au@sssnet.com>
> To: <tentec@contesting.com>
> Sent: Thursday, February 13, 2014 8:06 PM
> Subject: Re: [TenTec] Ten Tec Centaur 411 10m Mod Needed
>
>
>> At 02:48 PM 2/13/2014, Kris Merschrod wrote:
>>> I did the mod from the schematic and parts that T-T sent on a perfboard -
>>> it really isn't much, but, before hand, I pulled the 15 meter filter and
>>> put in a jumper wire - it worked like a charm w/o the filter - I am not
>>> sure what the harmonics on that looked like - others can do the hi-tech
>>> work :>)
>>
>> Ooops... there goes the FCC type approval.. ;-) (hope your antenna was
>> selective)
>>
>> Perry w8au
>>
>>
>>
>>
>>
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|