Post by HighMountainRadio on Mar 23, 2018 18:50:50 GMT -6
Good Evening Tester !
I'm glad that you found the info to be as interesting as I did ! There is some very handy information there at that site ! The furnace job is about 95% done, tomorrow we will finish it up. I'm glad that is all but over ! I'm exhausted ! Beating a hole through the cement wall for the power vent really tired me out ! Yes, I would use the solid copper board and rather than use an Xacto knife to cut away the copper to form the pads, although this is doable, I found it quite a lot easier to use a Dremel tool using an engraving bit or similar to cut away the required copper material. It also helps prevent you from cutting your fingers off or at the least, enduring a nasty laceration ! It is pretty easy to slip when carving away copper cladding.
I like using FR4 Glass Epoxy Fiberglass circuit board material, a bit thicker than what is typically utilized, it makes for a very sturdy, robust board. I will poke around for coil winding data that may make it easier to wind your own, I usually do. My good friend winds all of his own coils and even made a very cool jig to facilitate nice, even, uniform windings, very professional results ! I'll check with him and see if he likely has what you need in the way of reference material for coil winding. I'll message you here tomorrow afternoon. I am going to hit the sack after a little TV, I am beat !
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"
A very easy way to bring your 25mw Ramsey all the way up to 30W in one stage is to use a Mitsubishi amplifier module. These are pretty easy to assemble because they have all the matching circuitry inside the module. All you need to do is find a PCB for the amp module. You can find these on ebay for cheap from China and they come with all the components on the board. All you need to do is solder the module onto the board, provide a heatsink and power source and you are good to go. They operate at 12-13.8V and are not very efficient (about 50%), so you may want a 100W power supply just for some headroom. A meanwell is recommended. You will also need a low pass filter.
There is one downside to this approach. They don't make on of these modules that works from 87-108, but the low end of the band can be done with the RA30H0608M and the upper end with the RA30H1317M. I have only tested the low end (87), but in theory the upper end of the band should work with the other module. If you're right in the middle of the band, it may not work too well (maybe 15-20W), but that's still much better than what you have and worth a try. They aren't too cheap though, unfortunately.
These boards are not perfect for your application, though. For example, if you use the second board, you need to bypass the input attenuator and the RF switch (big blue relay box). The first board SHOULD work fine without any modifications, but for some reason the listing only mentions the RA30H4047M module. Because the matching is internal to these modules, it should work anyway and I think the seller was just lazy in the listing and didn't mention the other modules it can be used with.
...hooked up to the module to give a 30W TV station.
Searching "blonder tongue modulator" on ebay comes up with some cheaper options, but you never know what you're going to get because these are used surplus and you have to make sure you get one that covers the correct channels.
So yeah, I'd really recommend building one of those modules because you can use it for this purpose as well if you're ever interested.
"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 Mar 31, 2018 15:05:36 GMT -6
Greetings Tester !
I just installed my 3 element folded dipole antenna here at High Mountain Radio and I am very pleased to report that it is working fantastic ! I have absolutely NO reflected power and have 70 watts output into the antenna using the coaxial impedance matching method described in detail in another forum post here. It is giving amazing results, I HIGHLY recommend it ! See included pix of the antenna on the ground and in the air here.
73... Spooky...
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"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"
Spooky, I think i finally understand the 1:1 balun, it's there to turn the signal 180 degrees out of phase. i attached an image of how i understand the system working. I'm so stoked to understand now. Can you provide a link to get that sort of antenna? also, is the 6x6 loop of cable still needed for this type of antenna?
I think I could underpower that circuit and it would be a buffer to bring the FM30b up to half watt so the amp can get the power it needs. I gotta get an output filter though, I don't want to potentially screw up the nearby airport.
Cool Tester ! At a quick glance, it looks to be just what the doctor ordered ! Nice documentation it appears ! I just woke up and not banging on all 4 cylinders yet so I will look it over very carefully in an hour after my first coffee and smoke ! lol ! Btw, if you don't mind mentioning here, how far are you from Harrisburg PA (roughly) ? Don't mention your exact location, just a rough estimate will suffice.. don't mention in what direction from Harrisburg either for obvious reasons ! It is imperative that you fabricate the impedance matching balun (pre-calculated section of coaxial cable) from the exact same coaxial cable as your antenna feedline ! It can be ANY 50 ohm coaxial cable other than your feedline type, but the CRUCIAL characteristic is that both the coaxial cable feed line and the fabricated balun be the EXACT SAME 'Velocity Factor' (VF=The rate at which the RF signal propagates through the coax) !! ***NOTE: The antenna at the top of my antenna stack that is pictured here is the EXACT $14.95 special ! ***NOTE: I don't recommend using this particular antenna (the $14.95 special) in harsh winter/highly windy climates such as the far northern states but it will be perfectly robust enough for most any other weather environments, including those that experience winter snowy and sometimes icy weather. I have used antennas that were not even built THIS well for 20 to 30 years and never had any weather related damage !
Here is the link to the $14.95 3 Element Folded Dipole Yagi Directional Antenna on EBay, fantastic bargain ! I plan to buy 10 more of these to modify and resell soon..
The picture on the EBay ad sucks but I have included a couple of pix of the actual antenna used here to give you a better idea of it's construction. It comes completely re-assembled and all you must do is fold out each antenna element and snap it into position. Remove the receive-only 75-300 ohm matching transformer and replace it with the coaxial balun I have described and you will be good up to 500 watts without a problem !!! I have tested this antenna with homebrew 4:1 ratio balun at 500 watts and it will hum along happily for years, even at the 500 watt RF power level ! (assuming you are using either RG-9913 coax, or RG-8/U coax. I HIGHLY recommend Belden RG-9913 coax (Very low loss) or Times Microwave LMR400 coax, also very low loss coax ! But, even if you don't use either of those, use the best quality coax your budget can afford, rated at the power level you wish to broadcast with.
"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"
Spooky, I think i finally understand the 1:1 balun, it's there to turn the signal 180 degrees out of phase. i attached an image of how i understand the system working. I'm so stoked to understand now. Can you provide a link to get that sort of antenna? also, is the 6x6 loop of cable still needed for this type of antenna?
Thanks! "Tester"
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Greetings Tester !
Actually, it is technically a 4:1 impedance matching balun, not 1:1.. If you work the mathematics of it, you will find that it may seem incorrect, but this is the industry standard, tried and true method that is guaranteed to work ! Incidentally, I have absolutely NO reflected power at all ! A perfectly 'flat' VSWR ! I will elaborate shortly to describe the mathematics that makes this great method the ideal cheap way of matching 75 to 300 ohms that is good for 500 watts easily ! Just woke up so once I am fully awake after a major caffeine intake, I'll do a follow up for you ! By all means, keep in touch ! Feel free to message me at my listed e-mail address listed on this forum ! More to follow after the caffeine kicks in !
If we can take our discussions off-line of the forum, over to e-mail correspondence, I can provide much better detailed info and we won't be limited to the 3 picture limit of the forum, but I truly do understand if you may rather not do so !
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"
Spooky, I think i finally understand the 1:1 balun, it's there to turn the signal 180 degrees out of phase. i attached an image of how i understand the system working. I'm so stoked to understand now. Can you provide a link to get that sort of antenna? also, is the 6x6 loop of cable still needed for this type of antenna?
Thanks! "Tester"
ATTACHMENTS:
Hi Tester !
Your pictorial image is right on the money ! This is known as a 4:1 'balun', otherwise known as a coaxial impedance matching balun'. If you do the math, it looks like it actually matches 50 ohms to 200 ohms, but don't let that throw you. It does actually match the 50 to 300 ohms.. That thru me a curve at first but my very good friend who is an an antenna engineer explained it to me and said this has been the industry standard for ions and, "not to worry' it WILL work properly. And, it surely DOES !!! I have a perfectly 'flat' VSWR and when I measured the RF at the antenna feed point, ALL of my 75 watts, minus the characteristic loss in cable length is all there ! I now have a good 30 miles circumference of solid coverage !!!
I think there is some way to derive my e-mail address someplace here on the forum, so if you'd like, please feel free to e-mail me there and we can carry on.. I know another user of this forum was able to find my e-mail addy here so I will investigate how to find it and will let you know, if I can't figure out how, I will ask Kage..
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"
if you don't mind mentioning here, how far are you from Harrisburg PA (roughly) ? Don't mention your exact location, just a rough estimate will suffice..
I live about 700 miles northwest of Harrisburg... near a particularly windy city. I think it's still worth giving the old girl a spin on my mast
So I ordered the - i'm going to move my frequency up to 106.5 since it's pretty empty in my area, and closer to the advertised frequency... To power the chip, i ordered this - but they sent me this instead. it looks like it will still work with the RA30H1317M , I've got a 5 watt kit from china too, i think I will be able to use that as my exciter. I'll let you know how it goes
Post by ogrevorbis on Apr 19, 2018 20:25:55 GMT -6
Hey,
Glad to hear you're at the upper end. This means you also have the ability to use the RA60H1317M for 60W output (this one needs 50mW input instead of 25 - which you should have if you use the Chinese preamp like you said). This is the highest power module they make.
*** If you've never built an amp there is something important to note: Remember, before you solder the amp module, power the board and check the second pin from the input with a voltage meter. Adjust the blue pot with a screwdriver until it goes all the way down. Now solder the module. Antenna, power on, input power, then slowly raise the pot until the power needle on your output meter almost stops at the max (it will never completely stop and eventually it will break the amp if you keep going). You can check the datasheet for gate bias voltage or gate threshold voltage (something like that) and it should give you a good range for the voltage. The power to the module is simple just 12-13.8V.
More about the board (looks like you got the one with the relays): Interestingly none of the Chinese boards seem to include the bare minimum board for transmission only. The board you have with those blue relays is designed to be used with a transceiver (it will still work). The way you are going about it is OK, and should work fine, however if you want to maximize efficiency and not use the Chinese thing at all, you can do it by removing the three resistors right after the blue input relay. Solder your input coax right at the leg of the amp there and it will drive directly from the Ramsey. This is nicer. Looking at the picture, you will need to find a pad to solder the ground of the coax somewhere. You could probably use one from where the resistor used to be.
So I ordered the - i'm going to move my frequency up to 106.5 since it's pretty empty in my area, and closer to the advertised frequency... To power the chip, i ordered this - but they sent me this instead. it looks like it will still work with the RA30H1317M , I've got a 5 watt kit from china too, i think I will be able to use that as my exciter. I'll let you know how it goes
Greetings Tester !
Yes, please DO let me know how that works for you, I was eyeballing this little module a while ago when another person was asking me the best approach to take in order to boost his output RF power.. I would be very interested in knowing how it works as well as any personal comments pertaining to it !
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"