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|Need help/info about a low pass filter; Is it wise to connect one anyway?|
|Tweet Topic Started: 17 Oct 2012 - 18:42 (793 Views)|
|Gert||17 Oct 2012 - 18:42 Post #1|
19 Charlie Tango 006
At this moment I'm very busy designing my new base station to become. I just moved to a new place and I have to start all over again after quite a few years of absence on 11 mtrs.
My very first choice in aerials would be the Sirio Gain Master because of it's performance and very low TVI. The only problem is that I'm not able (allowed) to mount it because of it's length. Therefore it's probably going to be a Solarcon (Antron) A99. I've owned three of them in the past and I must say that they've always performed very well, at least compared to what you could expect of a half wave GPA. Despite that, unfortunately this antenna is also known for the "bleeding" of harmonics, a.k.a. TVI....!!
That's why I'm considering to purchase a low pass filter. I've been browsing the internet and I came to two potential options:
- RF Limited DF 3000
- MFJ 704
Both cost (approx.) 70 Euro's here in The Netherlands.
I've never worked with a low pass filter so I surely can use some advice. Is it wise to connect one in the first place? I mean: everyone has digital TV over here, but of course there will always be transistor radios, PC speakers and other stuff that could pick up my ssb activities...
I know that I could also get rid of the problem by mounting an "ugly balun" but I really wouldn't know how to make one and (next to that) that would only make the harmonics disappear which are coming straight from the antenna. My coax will be about 30 meters (!) long and it's running straight through my appartment building, so that's why I think it would be better to make sure that a clean signal will be sent to the aerial, since the coax is a part of the aerial installation as well. (The cable will run through a rain pipe and passes some neighbours.)
Does anyone have any experience with one of these two filters? Or does anyone have some other suggestions?
Oh yeah: I will mainly be pushing original RF power (30 W), with the option to insert my Zetagi BV 130 (200W).
Thanks in advance for your comments and/or advices!
19-CT-006 / Gert
P.S.: Excuse me for possible typographical or grammatical mistakes, but after all I'm Dutch right?
19 CT 006|
Hillegom - The Netherlands
|VoG||18 Oct 2012 - 12:39 Post #2|
Persona non Grata
 When I first used an A99 for SSB, my Voice could be heard on any telephone being used in my house. I tried: installing a low-pass filter; I tried relocated the aerial, tried changing the co-ax, I tried relocating my shack within the house and even tried using a different, brand-new, telephone. Nothing stopped the SSB Voices. I then fitted an Air-Choke and the Voices were gone instantly.
|Gert||18 Oct 2012 - 18:37 Post #3|
19 Charlie Tango 006
Thank you VERY much for your outstanding (and very complete) info about this topic!
Of course I'm going to use RG 213. In fact, I have to use that one because that's the only one that will be rigid enough to push it through that rain pipe with all of these tricky corners and angles.... (take a look at my situation in the attached drawing). That is my major concern by the way but I hope I will manage it.
As far as the A99 concerns: if I'm going to mount that one I will certainly take your advices. I told you already that this antenna is a compromise because the aerial that I really want to install is a Gain Master. However the local government has restrictions for antenna length, which is 5 mtrs max. But you know what? Maybe I'm just going to be an anarchist and mount a Sirio after all! In that case I don't have to worry about TVI at all because this aerial is well shielded with it's embedded choke coil. I could combine that with a low pass filter.
I'll keep you posted.
Many thanks again for your reply!
Edited by Gert, 18 Oct 2012 - 18:57.
19 CT 006|
Hillegom - The Netherlands
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