This is very helpful and practical. How many stubs do you actually have? I am
very curious how they all fit in a metal can. Do you mind sending me a few
pictures to get a better idea?
Rudy N2WQ
Sent using a tiny keyboard. Please excuse brevity, typos, or inappropriate
autocorrect.
> On Jul 26, 2016, at 10:37 AM, Jeff AC0C <keepwalking188@ac0c.com> 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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