[CQ-Contest] Coax Stubs for SO2R

Tue Jul 26 10:52:18 EDT 2016

I agree,
If I have 5 bucks invested in my stubs I'd be amazed!
And as shown before for less than 5 bucks they seem to work awful well.
https://youtu.be/wgn_L_LUXcI

Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 7/26/2016 9:37 AM, Jeff AC0C wrote:
> I would guess most guys don't go to this much effort. New stuff and 
> optimized placement?  Wow, that would be cool!
>
> I built the stubs up on an as-needed basis with whatever I had laying 
> about; there's no LMR400 around here.  It's all RG-11 or 213.  213 has 
> a bit better attenuation dip and is more rugged. All of the T 
> connectors were Chinese specials initially and later most were swapped 
> with AMP parts that I ran across at swaps and hamfests.  Never blew up 
> a Chinese one though so can't say the 50 year old AMP are better.
>
> The stubs are hanging off of the existing tower-based 2x6 antenna 
> switch which feeds a bunch of monobanders so no additional switching 
> was needed.  I did not optimize the placement; had room for them and 
> it was easy to do so they went out there.
>
> They live in a metal trash (no UV/mouse problems like plastic) can 
> which is staked to the ground (so it does not blow away in the big 
> winds we get). There is a foot of some sort of Styrofoam stuff at the 
> bottom so if the thing ever starts taking on water for some reason, it 
> won't leave them swimming.  Although if you seal the stub ends, it's 
> not a problem either.  I went with the metal after going out one time 
> to check how the stuff looked before fall and found my stubs tub half 
> full of water.  I think that was a week or two after CQWW RTTY one 
> year...  Got lucky nothing blew up there!
>
> I measure the isolation with a vna at the shack.  If I think I need 
> more attenuation, then I build another stub and grab a 1/8 wave (or 
> whatever is close) to space it away from the current one and turn my 
> single stub into a pair.
>
> I don't hear my other radios at all except on the 40/20m combo. Added 
> another stub and the level did not drop which is a possible clue that 
> there may be something on my 40m 4-square that's generating it's own 
> harmonics when hit with some power (which if you have seen my 4-square 
> you can EASILY believe that...).  I do have a set of 5b4agn filters in 
> the shack that run between the amps and the rigs which are 
> autoswitched.  The filters do a decent job of cutting down on 
> interference and definitely keep the rigs protected, but the added 
> stubs take the situation from a "tolerable" case to a "I don't need to 
> worry where I am on the band" sort of thing, most of the time.
>
> Like anything in radio, if perfection is not required, costs and time 
> invested can be scaled back quite a lot.  Building a set of stubs and 
> finding the hardware is sort of a hassle.  But it's something you do 
> one time and enjoy for a long run.
>
> 73/jeff/ac0c
> www.ac0c.com
> alpha-charlie-zero-charlie
>
> -----Original Message----- From: Rudy Bakalov via CQ-Contest
> Sent: Tuesday, July 26, 2016 10:02 PM
> To: Joe
> Cc: Jukka Klemola ; cq-contest
> Subject: Re: [CQ-Contest] Coax Stubs for SO2R
>
> For me the important lesson learned from this discussion is that stubs 
> are not as easy as snip-snip you got yourself stubs. Deploying them 
> takes planning and careful testing. That is, takes a lot of time.
>
> I did a very quick back of the envelope calculation. In order to 
> achieve the same level of attenuation you need two sets of stubs. 
> Right there you have roughly 800' of LMR400. A 1000' spool is $450. 
> Then you probably have another $100 in connectors. $550 in materials 
> alone. And we haven't even made the stubs yet.
>
> Add the time to cut, trim, and crimp the stubs. Add the time to 
> properly position them along the feed line. I don't know how others 
> value their time, but I would rather spend it with the family or 
> operate the station than spend two weekends in a spiderweb of stubs 
> and severed feed lines.
>
> I also think proper stub placement is easier said than well done. 
> Think about it- the SO2R remote switch is at the base of the tower and 
> then the individual antenna feed lines go up the tower. You either 
> have to find the ideal location up along the tower or coil tons of 
> coax at the base.
>
> If you coil up all that coax at the base of the tower you need to 
> build some sort of a structure to hold it.
>
> If you decide to have it up the tower then you add significant wind 
> load surface to the tower. Not good.
>
> Of course, I may be over-engineering things, but I prefer avoiding 
> complexity.
>
> Rudy N2WQ
>
> Sent using a tiny keyboard.  Please excuse brevity, typos, or 
> inappropriate autocorrect.
>
>
>> On Jul 26, 2016, at 9:12 AM, Joe <nss at mwt.net> wrote:
>>
>> Really? 200+ Euros? And coax made homebrew stubs are not much 
>> cheaper? HUH?
>>
>> Joe WB9SBD
>> <CLEAN-IDLE-TYME-LOGO-120x96.jpg>
>> The Original Rolling Ball Clock
>> Idle Tyme
>> Idle-Tyme.com
>> http://www.idle-tyme.com
>>> On 7/25/2016 4:53 PM, Rudy Bakalov 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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