[K3PZN-List] Subject antennas on RV's (a.k.a. refereeing multi-band interference)
wx3b at yahoo.com
wx3b at yahoo.com
Fri Jan 29 08:48:32 EST 2016
Dear CCARC Multi transmitter enthusiasts (and that includes RV transmitters),
One of the most important considerations for minimizing interference between stations originates with the
HF tranceiver itself.
Selecting 'clean' HF transceivers goes a long way toward minimizing inter-station interference - even on the SAME BAND.
Curt WB8YYY is correct, bandpass filters on each station are imperative....and there are different quality bandpass filters.Dunestar fileters are good; W3NQN design are even better (more out of band attenuation).
We can use W3AO's famous field day setup of 20+ transmitters (where there are often 2 or 3 on the same band) to interpolate to a good multi-transmitter solution.
Here are their (not so) secrets:
1. They use antennas with a pattern. Yagis...or dipoles.
2. They line the antennas up so the "preferred direction" (due west) has the antenna elements sideways to each other for maximum attenuation.
3. They space the antennas such that the lower in frequency you go, the LARGER the spacing between the same band antennas.
4. They do not use off center fed antennas or antennas where the feed line also radiates intentionally.
5. They do NOT have one antenna 'looking' into another.
Rob Heath K1RH also helped pioneer an interesting field day configuration one year which involved a Force 12 C3S tribander, A Dunetar triplexer, and Dunestar bandpass filters.
The result was (3) separate operating positions, one for 10, 15 & 20, all with separate feed lines, going to ONE antenna. I believe Ray and Kerri may have also tried this in the past - what amazed me the most about this setup is the lack of any measurable interference between the 3 stations sharing one antenna.
A multi-band dipole or vertical could also accomplish this 'trick' with an HF triplexer and band pass filters as well.
73,
Jim WX3B
________________________________
From: Curt Milton via K3PZN-List <k3pzn-list at mailman.qth.net>
To: Ray Wright <kb3vwk at gmail.com>; Carroll County Amateur Radio Club <k3pzn-list at mailman.qth.net>
Cc: Curt Milton <wb8yyy at yahoo.com>
Sent: Friday, January 29, 2016 8:28 AM
Subject: Re: [K3PZN-List] Subject antennas on RV's
Yes in my judgment, which by the way is mostly FD experience, that should work. You will hear the second harmonic of the 40m rig if you tune there on 20m. but with that modest separation you should be fine. As I am not familiar with your radios, best to borrow the dunestar filters as that will give you so extra margin. maybe you remember when we operated 20m SSB and 40m CW from the RV -- the 40m inverted V was mounted on the same mast as the beam. and I remember operating without the dunestar on the 40m rig.
what won't work so well is doing both rigs on the same band -- even on different modes. when on the same band, there is no way to filter the noise created by the transmitting radio.
yes do remember a ham ticket is a learning permit. the key is to keep learning, and hopefully ask these questions before trying them.
73 CUL Curt
On Thursday, January 28, 2016 10:30 PM, Ray Wright <kb3vwk at gmail.com> wrote:
so with say a dunestar filter on each 100w radio into a vertical antenna at front and rear of rv one on 20m and one on 40m we should be safe from bleedover?
On Thu, Jan 28, 2016 at 9:47 PM, Curt Milton via K3PZN-List <k3pzn-list at mailman.qth.net> wrote:
Ray/Kerri
on two different bands you should be okay -- just separate the antennas as much as possible, and run a test at lower power before cranking up to 100 watts. if you can get a dipole for 20m up 25 feet or more it might work better than a vertical. how far apart the antennas must be depends upon the radios some.
also -- even better - borrow the club's dunestar filters -- this will give you a little more margin.
73 Curt
On Thursday, January 28, 2016 6:30 PM, Ray Wright <kb3vwk at gmail.com> wrote:
Thanks Curt and John
The hope was to have the eagle one vertical on the ladder rack set up for
40m and either another vertical eagle one set up on the ground for 20m or
maybe an inverted diapole for 20m set up as the second antenna to the
vertical on the ladder rack? Thoughts?
ray and kerri
On Thu, Jan 28, 2016 at 8:13 AM, Curt Milton via K3PZN-List <
k3pzn-list at mailman.qth.net> wrote:
> Possibly what you all are alluding to is sometimes called 'mutual
> coupling.' Two closely mounted antennas 'experience each other.' There
> are two effects -- change in the terminal impedance and distortion of the
> antenna behavior.
>
> I didn't get the picture if these verticals are used on different bands or
> the same one?
>
> The other question to ask is whether the radios will be okay with one
> antenna transmitting and the other receiving. I would very much worry if
> they are used on the same band -- there is possibility for damage if they
> are too close, and too close may not be easily to calculate at the
> extreme. If these are HF radios used on different bands, the band pass
> filters in the radio contribute some rejection -- and allows coexistence.
> Remember for example when we operated an inverted V below your tribandder
> at field day. We didn't have issues because they were on different bands
> -- and it helped also to have several feet of separation.
> I do think you can operate on different bands using verticals on an RV --
> but best to separate them as much as possible.
>
> As for winter field day -- sounds like cabin fever after 2.5 feet of
> snow. And burning some fuel just to stay warm. I don't know how popular
> it is in the northern reaches, even here. A QRP group does FYBO this time
> of year, but they are based in Arizona. I don't know, plenty of other
> activities one can do with radios indoors this time of year. Outdoors it
> just might be better to be moving, maybe on some cross-country skis or snow
> shoes that sitting using a radio.
>
> CUL 73 Curt
>
>
> On Thursday, January 28, 2016 7:19 AM, John Stephens <kc3fdl at gmail.com>
> wrote:
>
>
> Kerri,
>
> I had the same question a a couple of months back. So to answer the
> question, I contacted Dr. Ed Fong who had recently given a skype
> presentation to the CARA club on his Dual Band J-Pole Antennas. (By the
> way, it was VERY interesting and CCARC should do the same!). He actually
> has a patent on his J-Pole design. His website is
> http://edsantennas.weebly.com.
>
> His response was that it isn't the coax you need to be concerned with, it's
> the antennas. They will resonate between themselves. In order to prevent
> the antennas from resonating, 'in theory' (his words) they should be placed
> at least 1 wavelength apart from each other. For example, if you were
> setting up 2M antennas they should be placed no closer than 2 meters
> apart. There are some things you can do to mount them closer, like offset
> the height, but the physics and math are not trivial. Antenna for differing
> bands can be placed closer together, say a couple of feet, without any
> significant interference.
>
> Hope this helps.
>
> 73 de KC3FDL / John
>
>
> --------------------------------------------------------
> John L. Stephens // KC3FDL
> KC3FDL at gmail.com
> Latitude: 39.4927 Longitude: -76.8894
> MHGL: FM19nm
>
> On Wed, Jan 27, 2016 at 10:50 PM, Kerri Wright <kb3vwk at gmail.com> wrote:
>
> > Is possible to run two vertical antennas at the same time and location
> > with out harmful feedback on coaxial line. If so how defeat that
> problem?
> > ______________________________________________________________
> >
> > 73 de K3PZN Westminster, MD
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