[CQ-Contest] Coax Stubs for SO2R

Tue Jul 26 18:10:09 EDT 2016

A stub attenuates the pass band signal.
Please check your stub attenuation.

Measure the power without and with the stub; using a separate power meter.

About 10% power loss is barely acceptable.
5% is better; acceptable.

In case the power loss exceeds 10%, you might want to use better coax.

73,
Jukka OH6LI

PS.
I am thrilled to read all writings. This discussion is so much better than
any book.
I sent one duplicate message; PI4CC stub arrangement.
In Europe, we have some stations with really well presented station
engineering.
PI4CC is maybe the best.

2016-07-26 18:42 GMT+03:00 Joe <nss at mwt.net>:

> That coax was stuff that I wouldn't even use on 160 meters.
> Outside for decades with nothing on the ends.
> Strip it back and braid as well as center conductor BLACK!
>
> Scrape with a knife to make shiny copper show so solder will stick, and
> that it.
> The badly contaminated sure doesn't seem to effect it's effectiveness as
> seen in that video.
>
> Joe WB9SBD
>
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 7/26/2016 10:36 AM, Rudy Bakalov wrote:
>
> 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 at 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://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> <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://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>
> <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> <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://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>
> <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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