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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