Jerry,
OK...FB,
I'll read up on it.
73,
Lee
-----Original Message-----
From: Dr. Gerald N. Johnson <geraldj@weather.net>
To: tentec <tentec@contesting.com>
Sent: Sat, Feb 26, 2011 8:56 pm
Subject: Re: [TenTec] OII V2.044A
I don't have an Orion II. On my other radios I have used my own
designs,
one of which is at
http://www.geraldj.networkiowa.com/papers/speakerfilter.pdf
I have also used a Timewave DSP59+ but its not clean from HF hiss. The
DSP in my FT-857D is pretty good about filtering high frequency hiss.
73, Jerry, K0CQ
On 2/26/2011 6:32 PM, kc9cdt@aol.com wrote:
> So, what make/model filter do you use on the Orion II?
> To kill that darn high frequency hiss.
> 73,
> Lee
>
>
>
>
>
>
> -----Original Message-----
> From: Dr. Gerald N. Johnson<geraldj@weather.net>
> To: tentec<tentec@contesting.com>
> Sent: Sat, Feb 26, 2011 1:16 pm
> Subject: Re: [TenTec] OII V2.044A
>
>
> That's where I find my passive speaker filter shines. It passes no
> audio
> section noise and no IF noise, an few DSP HF artifacts.
>
> A fundamental of receiver design is that selectivity works best as
> close
> to the antenna as possible. Unfortunately that ignores the noise
> contributions of all the stages after that. The typical product
> detector
> is double sideband so the IF noise of the image is there along with
the
> signal and the RF noise that passed through the filter plus the same
> sideband noise much wider than the filter that was up front. Receivers
> would benefit from having a SSB filter at the product detector, but I
> know of only one design that way, called the Hohentweil, a 2m
> transverter kit. Then they would benefit from making the audio output
> stage, often essentially a power op amp into an active low pass
filter.
>
> In tube receivers a simple capacitor from audio output tube plate to
> ground combined with the tube and the audio output transformer to make
> a
> rudimentary low pass filter. In the 75S-3B, it was effective enough to
> make using 2125/2975 tones for 850 shift RTTY (and for all recorded
> history, the standard tones for 850 shift RTTY due to an AT&T
standard)
> difficult until the capacitor was removed from the circuit.
>
> 73, Jerry, K0CQ
>
> On 2/26/2011 11:57 AM, kc9cdt@aol.com wrote:
>> I think one of the reasons the Drake R-4B, Hallicrafters SX-117 and
>> many others are beter in a noisy condition is simply they do not have
>> all the high frequency respnse in the audio, or maybe it is the tube
>> amp??. I wish there was a HF cutoff on the OII, full EQ like Bob Heil
>> recommended day one to TT way back may have helped.
>>
>> Interestng...last nght, on 40 I was working a really nice guy in St
>> Kitt. There was quite a lot of QRN, He was just above the noise floor
>> I found that if I used the old Hallicrafers SX-117 to receive
>> him...copy was more clear!!!!
>>
>> OMG, Maybe we need to go back to the older stuff (I have both) Unless
>> of course it is contesting at a high level...where you need lot of
> speed
>>
>> I use the Collins S line& KWM-2
>> Drake C line (all Sherwood mods)
>> Halli SX-117/HT-44
>> Halli SX-115/HT-32B
>>
>> Along with the OII of course.....
>> 73,
>> Lee
>>
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