[CQ-Contest] Coax Stubs for SO2R

Tue Jul 26 14:13:09 EDT 2016

Go to W8JI.com  and check out Tom's info on proper tuning / loading of 
amps and particularly Heathkit amps and why some get destroyed.

73, Gerry, K8GT

On 26-Jul-16 09:14, Joe wrote:
> Can anyone explain, Say youre using a SB0220 amp.
> I have seen this many many times recently. Explain this.
>
>
> improper amp loading/tuning.
>
>
> Or better yet what is
>
> proper amp loading/tuning.
>
> Joe WB9SBD
>
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 7/25/2016 4:53 PM, Rudy Bakalov via CQ-Contest wrote:
>> Jukka, Jim, and Steve,
>>
>> Thank you for taking the time to go into details. What's clear to me 
>> that the non liner AB type of amps contributes significantly to 
>> harmonics along with improper amp loading/tuning.
>>
>> As I mentioned earlier I already have BPFs so now I am left with the 
>> mechanical challenge of stubs. Specifically, will have to follow 
>> Jukka's advice on adding coax between the remote SO2R switch and the 
>> antennas.
>>
>> Honestly, I even wonder if the hassle of building and placing two 
>> sets of stubs (it seems the opinion is that two are needed) is really 
>> that much cheaper compared to buying high power BPFs. Between Remo's 
>> filters and the link below there are affordable alternatives to 
>> Ranko's BPFs:
>>
>> http://www.antennas-amplifiers.com/Band-Pass-Filter
>>
>> For €1200 one can have plug and play filtering (although I may run 
>> into components' thermal properties when the filters are outside by 
>> the tower) that is not critical with respect to placement along the 
>> feed line.
>>
>> Who sad ham radio is a hobby; feels like serious engineering work to 
>> me :-)
>>
>> Thank you all for your patience.
>>
>> Rudy N2WQ
>>
>> Sent using a tiny keyboard.  Please excuse brevity, typos, or 
>> inappropriate autocorrect.
>>
>>
>>> On Jul 25, 2016, at 4:41 PM, Jukka Klemola <jpklemola at gmail.com> wrote:
>>>
>>> Hi,
>>> I try give simplified answers ...
>>>
>>> This should answer also Rudy's question.
>>>
>>>
>>> 2016-07-25 15:47 GMT+03:00 Joe <nss at mwt.net>:
>>>
>>>> This also puzzles me.
>>>> OK if an amp because of it's tuned matching circuits, block out of 
>>>> band
>>>> energies
>>>
>>> Amplifier circuits attenuate unwanted band energy.
>>> But to a limit.
>>> A Pi filter attenuates to some level, Pi-L attenuates more.
>>> If that is not enough, we need additional attenuating, that is 
>>> additional
>>> filtering like a stub
>>>
>>>
>>> The why do we have these energies at all in the first place?
>>>
>>> When amplifying a signal in an amateur amplifier, the plate current 
>>> when
>>> only PTT is activated is less than a quarter of plate current with 
>>> maximum
>>> specified signal that is amplified.
>>> It means there is plate current through most of the sine wave signal 
>>> cycle,
>>> but not all of it.
>>> It means there is a sharp corner in the output signal .. it is not a 
>>> clean
>>> sine wave.
>>> Such signal with such corners has harmonic energy.
>>> This energy propagates towards the antenna connector.
>>> It travels through the output circuit; most often Pi or Pi-L.
>>> On an oscilloscope, the signal looks pretty much like a sine wave 
>>> but it
>>> contains harmonic energy.
>>>
>>> Sorry, but this gets more complex when digging deeper.
>>> Next step would require you to read some books or at least web sites.
>>>
>>> Easy to understand information packages are ARRL hand book and 
>>> Orr/W6SAI
>>> Radio Handbook.
>>>
>>> ARRL handbook is easy to find and purchase.
>>> I would suggest to try and find also a paper book:
>>> http://www.eham.net/reviews/detail/3963
>>>
>>> W2VJN book is a must if you want to understand more about RF filtering
>>> needs at a multi radio station.
>>>
>>>
>>> ** Encouragement, keep it simple message:
>>> As we are hams, we can use ready made recipes for stubs, among many 
>>> other
>>> things.
>>> That is allowed for us and us hams, we can just accept many things 
>>> as given
>>> facts.
>>>
>>>
>>> Does not a Radio have the equivalent of an "Exciter" ( the ummm low 
>>> level
>>>> driver )
>>>
>>>> And the "AMP"  ( the final output amplifying system )
>>>>
>>>> So, if all this filtering is happening why do we have spurious out 
>>>> of the
>>>> radio, but not an amp?
>>> There are a lot more signals in the radio than the mains input and RF
>>> connector with RXinput / TX output.
>>> To start with, the radio's oscillator is not on your actual output
>>> frequency.
>>> There are other oscillators, mixers, filters, amplifier circuits, more
>>> filters and so on inside your transmitter before the antenna connector.
>>> All those are creating or limiting spurious signals and we need to 
>>> engineer
>>> the radios so the radios do not emit unnecessary signals and we 
>>> engineer
>>> our radios so they do not input unnecessary signals or at least the 
>>> radio
>>> does not care about the unnecessary/unwanted signals.
>>> Emissions are emissions; intended or spurious.
>>> The receiving side phenomena are under words immunity or 
>>> susceptibility.
>>> Together they are electromagnetic compatibility EMC.
>>>
>>> These spurious signals propagating from device to another device can 
>>> be as
>>> bad as K1EA described about the radios they used.
>>> The radio2radio signal propagation happened on a set of phenomena 
>>> caused by
>>> some radio internal signalling leaking through radio wiring and 
>>> propagating
>>> to another radio so the receiver of the other radio heard the 
>>> transmitting
>>> radio signal regardless the frequencies the radios were on,
>>> That is a really puzzling situation and typically difficult to 
>>> overcome.
>>> Most likely the leaking and injecting mechanism was through antennas
>>> connected to radios but not necessarily. That kind of electromagnetic
>>> incompatibility should be rare, though.
>>>
>>> After Ken K1EA et al added RF and maybe also other filtering, the 
>>> radios
>>> stopped hearing each other that badly.
>>>
>>> Other filtering are for example ferrites we place on DC power cords, 
>>> mains
>>> wires and other .. PTT / band data and any other wiring you have at 
>>> your
>>> station. We attenuate unwanted signals until they do not bother us.
>>> You can find a lot of information about different kinds of filtering 
>>> in the
>>> internet.
>>>
>>> All cases are different.
>>>
>>> Some hands-on information here:
>>> http://wiki.k1ttt.net/Default.aspx?Page=2008%20Maintenance%20and%20Upgrade%20Blog&NS=&AspxAutoDetectCookieSupport=1 
>>>
>>>
>>> Look for words
>>>   -harmonic
>>>   -power
>>>
>>>
>>>
>>>> Joe WB9SBD
>>>
>>> 73,
>>> Jukka OH6LI
>>>
>>>
>>>> Sig
>>>> The Original Rolling Ball Clock
>>>> Idle Tyme
>>>> Idle-Tyme.com
>>>> http://www.idle-tyme.com
>>>>> On 7/25/2016 5:48 AM, Rudy Bakalov via CQ-Contest wrote:
>>>>>
>>>>> Jukka,
>>>>>
>>>>> It is the statement below that really puzzles me. All amp people I 
>>>>> know,
>>>>> including those that manufacture commercial amps, categorically 
>>>>> state that
>>>>> amps do not generate harmonics on their own. That is, amps merely 
>>>>> amplify
>>>>> them.
>>>>>
>>>>> To me this seemingly minor difference is huge. If amps only 
>>>>> amplify but
>>>>> do not generate harmonics then there is no scientific reason for 
>>>>> filtering
>>>>> after the amp assuming the same amount of filtering is applied 
>>>>> before the
>>>>> amp. In practical terms, this would mean that low power BPFs 
>>>>> before the amp
>>>>> are as effective as high power BPFs after the amp.
>>>>>
>>>>> The key point here is GENERATE vs AMPLIFY harmonics. Can the average
>>>>> commercial, well stabilized amp generate harmonics?
>>>>>
>>>>> Rudy N2WQ
>>>>>
>>>>> Sent using a tiny keyboard.  Please excuse brevity, typos, or
>>>>> inappropriate autocorrect.
>>>>>
>>>>>
>>>>>> On Jul 24, 2016, at 5:14 PM, Jukka Klemola <jpklemola at gmail.com> 
>>>>>> wrote:
>>>>>>
>>>>>> In case you do that, you still need stubs after the amp.
>>>>>> Amplifier creates harmonics out of the fundamental frequency.
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