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Re: [CQ-Contest] Coax Stubs for SO2R

To: Joe <nss@mwt.net>
Subject: Re: [CQ-Contest] Coax Stubs for SO2R
From: Rudy Bakalov via CQ-Contest <cq-contest@contesting.com>
Reply-to: Rudy Bakalov <r_bakalov@yahoo.com>
Date: Tue, 26 Jul 2016 11:36:28 -0400
List-post: <cq-contest@contesting.com">mailto:cq-contest@contesting.com>
How do you guys do that? That is, how do you end up with all that coax without 
buying it? Or the connectors? I have purchased about 500' of LMR600 and maybe 
another 500' in LMR400 Flex. The Big Bang didn't pile up any coax in my back 
yard :-(

Rudy N2WQ

Sent using a tiny keyboard.  Please excuse brevity, typos, or inappropriate 
autocorrect.


> On Jul 26, 2016, at 10:52 AM, Joe <nss@mwt.net> wrote:
> 
> 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
> <CLEAN-IDLE-TYME-LOGO-120x96.jpg>
> 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@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@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@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@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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