Hello, I am a noob when it comes to this stuff so please have mercy on me. I recently bought a CZE-15A transmitter which I plan to use to broadcast on the frequency of 92.7 Mhz. My question is, what antenna should I use, and how should I build it? I was looking at 1/2 wave and 1/4 wave antennas, and I noticed that people called them 1/2 wave dipoles, 1/2 wave GP antennas, and just plain 1/2 waves. Is there a difference between all of these? I know that the 1/2 wave dipole is fed in the center, so does that mean the GP antenna is end fed and has radials on one end, and the plain 1/2 wave is also end fed with just 1 whip and no radials? If you couldn't tell, I am mixed up with all of this terminology, and any help would be appreciated. Thanks!
Post by HighMountainRadio on Apr 21, 2018 19:26:44 GMT -6
Greetings Nic !
I am very busy with a time sensitive project right now, but, tomorrow morning, I will be very happy to give you a synopsis of each antenna, type, thorough explanation of the structure of each, how they are fed, along with the advantages of each type, etc.. Check back here tomorrow about 10:00 AM EST and your answers will be waiting for you here ! Until then, take care, and I look forward to assisting you !
Until then, 73, and have a good evening ! Spooky... @ High Mountain Radio...
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
I have done some thorough reading and thankfully was able to puzzle out most things on my own. I have decided on building myself a j-pole antenna, which is what quite a few people on this forum suggest from what I have read. I am going to head out to a hardware store tomorrow and get myself some 1/2 inch copper pipes cut to size and hopefully get everything soldered up. One big question I do have left, is that while the calculators I used tell me the optimal position to attach the coax to the antenna, I have no way of measuring the SWR as is. Do you think I can trust the calculators without using an SWR meter for testing? Also, how many turns should I have in my balun and what diameter should I make it?
Post by HighMountainRadio on Apr 22, 2018 5:01:14 GMT -6
I would trust the calculations given for the j-pole, you should be able to get close enough to a match that way for now, however, at your earliest possible convenience, I HIGHLY recommend obtaining a suitable VSWR (SWR) meter and measuring the reflected power to ensure maximum performance and to be certain that no significant amount of RF power is being reflected back to your transmitter because of a mismatch situation, which has the potential to damage your transmitter's final RF power output device !!! I commend you on your decision to build your own antenna !! I always encourage folks here in this forum to fabricate their own antennas and anything else that they are capable of ! It serves as a GREAT educational experience ! Also, worth mentioning, VSWR measurements SHOULD be performed at the antenna feedpoint instead of at the transmitter end of your transmission line for accuracy ! MANY folks measure it at the transmitter, which is better than not at all, but measurement at the antenna is the PROPER method !
You may purchase a decent, useable 'SWR/Power Meter' on EBay for a reasonable price, BUT, ensure that it's specifications state that it is capable of operating between 88 and 108 MHz !!! VERY important, as not all of them are capable and are only good up to 30 MHz or so ! If you plan on doing a substantial amount of work with antennas, transmitters and transmission lines I recommend you invest in a excellent quality instrument. I utilize a broadcast industry standard Bird, Model 43 instrument with the appropriate 'element' calibrated for the power level and frequency of operation I am working with. It will measure VSWR and RF power very accurately. Look it up on the web and read it's owner's manual to get a clear understanding of it and the overall cost. You can readily find pretty decent deals on EBay for used Bird 43's in good condition as well as any required 'elements' commonly referred to as 'slugs'.
For now, if you may be able to borrow a meter capable of accurate measurement within the FM broadcast spectrum, from someone that would be highly recommended ! You may be able to borrow one from a local CB radio shop or Amateur Radio operator, commonly known as 'ham' radio.. Many if not most 'hams' own a Bird 43, 'THE' RF industry 'standard' ! If you can't locate one right now for your J-Pole project, yes, just go by their recommended specification for the matching mechanism point of attachment for initial testing purposes but SURELY, do buy or borrow a suitable meter ASAP to get an accurate indication of the actual VSWR, IMPERATIVE !!!
As far as the balun, I am attaching a picture of you to construct it for your assistance in the correct method of construction. The balun should be 6 turns, would into a 6 inch circumference, although not extremely critical, and it is imperative that you utilize the balun to assure that no RF is radiated along the length of your transmission line !! VERY important !! The balun should be attached at the antenna feedpoint ! I cut small pieces of flat wood to serve as 'form retaining spacers' to assist in keeping each of the loops of cable adjacent to each other, also very important for proper balun performance ! I secured the wooden spacers using several wraps of electrical tape.
This was a 'hurry up' fabrication of mine, I plan to fabricate another, much more professional looking model soon. It should be noted that using this balun and cutting my Ground Plane antenna to the correct length for my operating frequency, I achieved a PERFECTLY 'flat' VSWR, a perfect 1:1 match with absolutely NO reflected power back to the transmitter ! I'll send you a detailed message on the various antenna types and the benefits of each different type here in a short while after I wake up a bit and have my customary cup of coffee I always have first thing
in the morning, mandatory for me ! lol ! I used a homebrew Ground Plane' initially with very good results and then replaced it with a purchased 3 Element Folded Dipole Yagi type antenna that was meant for FM Radio Reception and as it came to me was made to be mounted horizontally, but with a very small amount of work, I modified it for use as a directional broadcast antenna by drilling two holes for the U-Bolt mast mount hardware about 2 inches away from the original holes into the other side of the antenna boom so that it could be mounted vertically, the desired method utilized in mostly ALL pirate stations.
The broadcast standard type of antenna that is BEST, is a 'right-hand circularly polarized' antenna, however, the commercial models available from many sources, including Chinese sellers on EBay, are quite expensive ! I had the very good fortune of acquiring a '2 Bay circularly polarized' antenna array, comprised of a pair of Shively Model 6812B 'CP' antennas that came to me already setup and tuned to 99.5 MHz, very close to my frequency of 99.9 MHz ! Through a very good friend who is a FM radio and television broadcast engineer for a regional university, I luckily obtained these antennas for FREE !!! Although they are over 10 years old, they are still in 100% perfect condition, including the protective 'radomes' that are included as well as right down to the high quality stainless steel bolts used throughout, not one iota or hint of rust or weathering at all ! Even the exterior of the radomes exhibit no signs of UV damage or discoloring attributed to ultraviolet radiation from sunlight ! Simply amazing !!
I plan to erect these antennas very soon here in order to follow the standard antenna choice used by the majority of FM broadcasters, in order to observe their performance compared to both the Ground Plane and 3 element folded dipole yagi antennas.
One more helpful hint that I highly recommend is, when setting up your final antenna configuration that you choose to utilize, ALWAYS use high quality BLACK, Ultraviolet impervious tie wraps (zip ties) when securing your cable and anything else where you may utilize them !! You will be doing yourself a BIG favor, especially over the long term, far less maintenance required ! You can purchase them at Home Depot (although fairly expensive there) or a number of other sources, I would suggest EBay, purchase from a reputable seller that has many sales and a 100% or close, feedback rating to ensure that you get the 'real deal', genuine UV impervious zip ties ! You will get your best price purchasing them from an EBay seller !
73, Spooky...
Attachments:
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
Post by HighMountainRadio on Apr 22, 2018 7:35:24 GMT -6
Greetings Once Again From 'HMR' Nicc !
I am sending you this message here, since I cannot seem to directly attach any images when directly messaging you here on this forum. I've attached images of my currently utilized 3 element folded dipole yagi antenna that I bought for $14.95 plus $15.65 shipping from a guy on Ebay, he has a pile of them still for sale of the same model, I am going to buy a few more soon before they are all gone. I will keep one for a spare replacement if it ever becomes necessary, the remainder of them. however many I buy, I will offer for sale, modified and tuned for FM broadcasting, they can easily handle power levels up to 300 watts EASILY utilizing the impedance matching balun that I fabricate for the purpose.
I have built MANY antennas over the numerous years I have been playing with radio, built and tuned for other bands and frequencies ! I've been at it for over 50 years, I am somewhat older now.. lol !
Check out the images attached..
73, Spooky...
Attachments:
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
I am also very new to this, but would like to cover a 3km radius(size of my town). Or if you know of a good setup that would be able to reach or exceed this goal on a budget? I wouldnt want to spend over $250 Canadian Rupees on a transmitter and antenna, as I will have other costs to tend to.
1/2 wave dipole is simple and decent for most situations. Folded dipole yagi antenna like HighMountain posted is good if you want to direct your signal to a certain place. 5/8 wave ground plane or "Dominator" type antenna is best for high gain omnidirectional (all directions) in a flat environment. 1/4 wave ground plane - best for omnidirectional in a hilly or mountainous environment. (Unless you are on a mountain, in which case 5/8 wave is better).
I've come to find high gain is not really beneficial in a hilly environment; low gain works better for me.
I am also very new to this, but would like to cover a 3km radius(size of my town). Or if you know of a good setup that would be able to reach or exceed this goal on a budget? I wouldnt want to spend over $250 Canadian Rupees on a transmitter and antenna, as I will have other costs to tend to.
Thanks for any and all input!
Good Morning !
No, that is a DTV antenna and will not work for your intended purpose. I'll message you later regarding this subject. Got to head off to work now. I would have replied much sooner but I was having problems logging into the forum but I resolved that this morning finally.
73 Spooky
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
Post by HighMountainRadio on May 21, 2018 5:54:30 GMT -6
Greetings Nicc !
I use one of these to steer my signal to favor one particular town nearby but it's omni-directional characteristics really weren't affected significantly and I still have a VERY satisfactory signal in the other directions as well !!
See here, at $124.95 this is the bargain of the day ! It is an AWESOME performer and MUCH cheaper than the crap you find on Ebay at MUCH higher prices, even for simple dipoles !!
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"