Home made or manufactured?

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AronDouglas

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I've been looking at getting either the ST2 or the Diamond discone antenna for a while now but just recently came across the home made antenna on the RR wiki. This thread is not about which antenna is better per say, but rather how good is the home built antenna compared to the manufactured ones? I'm talking about wide band antennas (trying to compare apple to apples) such as long whips or discones. Is the home built antenna even in the same ballpark as manufactured antennas?
 

popnokick

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There are several home made / home built antennas discussed here in the RR forums and the RR Antennas Wiki. To which one are you referring?
 

br0adband

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Pretty safe to say (at least I hope it is considering the amount of research I've done in the past week on the Homebrew OCFD) that it's considered to be a somewhat good/somewhat mediocre performing antenna in general compared to actual tuned resonators but that's pretty much a given if you understand anything at all about antenna technology. For general purpose reception (not transmitting, obviously), the Homebrew OCFD will do "ok" across the given range which is commonly listed as from ~30 to ~800 MHz give or take a few - it's a very wideband antenna when built according to the wiki "standard" design.

Also pretty safe to say that the far far more knowledgeable folks about antenna design around here (hertzian, popnokick, etc) have stated multiple times across multiple posts in multiple threads that no, the Homebrew OFCD will not compare favorably against solid commercially available antennas of a similar nature aka wideband scanner reception antennas. Considering you can build a Homebrew OCFD for basically $10-20 and also that you can use it reasonably well inside a residence, in an attic, hanging in a window, and so on means you get an antenna that does work, maybe not to the levels the commercial ones can or actually do, it sure can't hurt to build one at some point and see just how well it performs for you.

I'm about to construct one myself here soon to see if I can improve upon my current situation which is basically SDR-centric reception these days using two RTL sticks, SDR# software, DSD+ (with DSD on occasion), Unitrunker, and the rather ubiquitous Radio Shack 800 MHz duckie along with the also rather ubiquitous Diamond RH-C77A dual band whip feeding into a cable attached to the RTL stick(s) using an MCX to BNC pigtail.

I'm located in a great spot in my area, in the center of most everything, with most of the major radio traffic taking place fired from repeaters that are on the mountain-tops that completely surround my area (I'm smack in the middle of it all, actually), up on the 3rd floor of my apartment building but but but.. I can't get an antenna on the roof so, I figure the Homebrew OCFD might help my situation given the reports by many other people that have built and continue to use them of how well they actually do work overall.

I suppose I should back up a bit with the "not as good as commercial hardware" line of thought and say that I'm stating that myself based on what I've seen the more knowledgeable folks say about the Homebrew OCFD. The consensus as I currently understand it is the Homebrew OCFD is way way better than any simple telescopic whip or duckie antenna included with most scanners so in that respect it's almost a must-build kinda thing for anyone (and considering the price, again, it's not like you're spending $100+ on it, regardless of whether you build the wire version, the copper pipe version, or one of the "shorty" variants).

I think it'll probably surprise me when I finally get around to building my own, at least I hope it will. Might build a second one, a "shorty" geared towards the MilAir band since I'm a few miles from Nellis AFB. I can barely get the ATIS from Nellis currently with the Diamond RH-C77A; I rigged up a cable to an SO-239 chassis jack and stuck a cut-to-300 MHz half-wave wire coat hanger homebrew and it makes a huge difference with the ATIS reception so I have high hopes for the Homebrew OCFD.

Can't hurt to build one, or two, or whatever I suppose.
 

popnokick

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Br0adband- My sentiments exactly... how can you afford to not at least try the OCFD wire version? As hertzian wrote, if it doesn't work for what you're trying to hear you can afford to say, "Oh well" and be out only $10-$15 and 30 minutes of your time.
I just put a two-port cable modem broadband amp on my copper-pipe OCFD in my attic. It's feeding two scanners and so far doing great. I've actually picked up at least one agency I haven't heard before, and have much more reliable VHF low and UHF now. And no intermodulation overload or other undesirable stuff.... however, I am in a very rural area very far from high-powered transmitters.
I'm going to take some pics and put them in a new post here on RR, along with some of the improvements I've noticed.
 

AronDouglas

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I know homebrew antennas are not going to outperform manufactured antennas, but the more I research the more I see people very happy with their homebrew antennas. And as you guys said (and many others), its $20 ish (or in my case free), you cant really go wrong. I look at some antennas and think that it cant be that hard to make something like that. Then I get a glimpse of the science behind a properly tuned antenna...lets just say thats not my field of expertise.

popnokick@ I was just referring to any wideband homebrew antenna.
 

LIScanner101

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In my case, it’s not a matter of how cheap the OCFD is. I’m not going to make one “just because” it’s only going to cost me $10 or $20. In my case, my PRIMARY reason is for portability. Sorry if I keep mentioning this, but I travel to the Bay Area pretty frequently. I have been able to build a “portable” Antenna Specialists MON-Series antennas (see my pics if you want for details) and it ROCKS even several feet away from the window of a hotel. On rare occasions I can actually mount it directly on the window railings and it’s even better out there (for obvious reasons), but as I said, it’s rare that you can actually open hotel windows more than a couple inches, especially when the window is on the 11th floor (locked due to liability issues). Even with the “portable” version I occasionally have a hard time with some TSA agents who are not too happy with the fact that I am carrying “steel rods” in my suitcase…..! SO, I’m going to build an OCFD and see how that works. Even if it’s “as good” as my packable MON I might just leave the MON at home from then on, as it will alleviate my occasional TSA woes. We’ll see.

With the OCFD I can see me taping it to the wall-length windows you get in some hotels, and running some premium quad-shield RG-6 coax to my scanner. If I can't tape it I can always hang it from the curtain rod.

PS – I came across some 10 AWG flexible insulated wire, I’m going to use that for the OCFD. It might not make much difference but I’ve been told that the thicker the “radial” of an OCFD are, the wider the bandwidth. 10 gauge wire is about as thick as I want to go for portability.
 

br0adband

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I know I'm going to expose my ignorance here - and I am very ignorant, but at least I know that much ;) - but can someone explain the idea of "bandwidth" with respect to the thickness of the wire or the particular radiator someone might choose when constructing an antenna (of any kind)? I've done some research and I see it mentioned quite often and for some strange reason I'm just missing it and not getting it in terms of exactly what the hell that term means in application with antenna radiator thickness.

I just read a post that was saying "Going from a 1/8 diameter rod to a 3/4 tube at UHF would be noticeable" from the thread here and I'm still missing it.

Sometimes it's the simplest things I guess that stump us the most... :confused:
 

AronDouglas

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I was just about to ask that very same thing, br0adband. I was going to make this Homebrewed Off-Center Fed Dipole - The RadioReference Wiki, and wanted to know if I could use 1/2 copper instead of 3/4. 3/4 just seams way too big given that most wideband antennas are maybe 1/2 inch thick.

LIScanner101, have you tried this antenna? http://www.qsl.net/n4yek/scanner/antenna.pdf I had a little extra time on my hands last night and built one :)

I may end up buying a manufactured antenna in the end, but building them is MUCH more fun.
 

LIScanner101

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LIScanner101, have you tried this antenna? http://www.qsl.net/n4yek/scanner/antenna.pdf I had a little extra time on my hands last night and built one :)

No, I don't really have any need for a base antenna, I have some really good ones at home :D (see sig). My primary need for building my own would be strictly for better portability. A wire OCFD is easy to pack and fly with, I don't think the TSA would like me carrying a ground plane antenna on board :lol: How did you like it, anyway?
 
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AronDouglas

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I like mine a lot...but thats because I built it :) I haven't had time to try it out yet, got to go order a PL-259 to BNC connector first.

The thing is actually fairly small. I'm going to find a way to make it portable, maybe just remove the ground planes. I'll see if I can get some pictures up.

The ground planes are 20 inches bent out at a 45* angle. The center tall antenna is 19 inches tall. And its all 10gauge copper wire. And the cool thing is that the whole antenna mounts on top of a PL-259.

I want to try and make the ground planes collapsible so its easier to transport.. And that is my Icon IC-R10 next to it for size comparison.



 
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LtDoc

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Want to get rid of those radials? Remove them and substitute a "rat's tail". That's just a simple wire the same length as the vertical part of the antenna that's attached to the outer shell of however the antenna attaches to the radio.
If the vertical element of that antenna is a 1/4 wave on some frequency, then adding a 1/4 wave "rat's tail" to it will turn it into a 1/2 wave antenna. Not going to be a huge reception difference, but there certainly can be an improvement. (A 1/2 wave antenna has no gain. A 1/4 wave antenna has a slight negative gain. So there's an increase in gain. Why that 1/2 wave doesn't have gain? Because it's used as the standard for measuring gain. 'Gain' is always in relation to some other antenna and the standard is a 1/2 wave.)
- 'Doc
 
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