--------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE200014 Date: 10/01/97 From: IVY IVERSON Time: 03:45am \/To: ROY WITT (Read 0 times) Subj: antenna thingy -=> On 09-29-97 08:45, Roy Witt said to Stan Black,<=- -=>"About antenna thingy...,"<=- -=> 28 Sep 97 17:50, Stan Black wrote to Jeff Edmonson: Hi, Roy; SB> So, do I hook up the shield and center conductor to the so-239 in the SB> normal way. And at the top, do I need a bare piece of wire as a SB> radiator? That's what I need to figure out. Don't want to be cutting SB> up my good coax for nothing! Thanks! RW> RW> You'll need a 1/4 wave stub at the top and a decoupling sleeve at the RW> bottom.. Quarter wave stub at the top? Are you referring to a whip? And a decoupling sleeve like so?: ||| <-bottom 1/4 wave element ||| ||| <-Bottom of antenna. (SO-239 optional) | ||| | | ||| | | ||| | <- 1/4 wave metal tube over coax | ||| | |_|||_| <- Connected to shield here ||| ||| <- Coax to xcvr ||| Correct? 73 DE KB9QPM Ivy ... Antenna... Isn't that Uncle Harry's wife? -- ,-----> Ivy's WALL BBS Home of Lakeshore Net <-----, |---------------> Ivy Iverson, KB9QPM <--------------| `-> Netmail me a request for info on Lakeshore Net <-' ___ Blue Wave/QWK v2.20 [NR] --- TriToss (tm) 1.03 - (Unregistered) * Origin: Ivy's WALL BBS - Sheboygan, WI 920-457-9255 (1:154/170) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE200015 Date: 10/01/97 From: IVY IVERSON Time: 03:55am \/To: ROY WITT (Read 0 times) Subj: High Gain Antennas for 2M -=> On 09-29-97 09:52, Roy Witt said to Ivy Iverson,<=- -=>"About High Gain Antennas for 2M...,"<=- -=> 26 Sep 97 16:13, Ivy Iverson wrote to Roy Witt: RW> Hello Ivy. Hi again, Roy; ... II>> Do you have construction details for this one? Would it be II>> possible to get a copy from you? RW>> You guys are just bound and determined that I go home and look RW>> through my garage file cabinet...:) II> II> Yup. (Pretty please?) }:-> RW> RW> See recent post on high-gain omni collinear in HAM-ECHO... Ok, I'll look in back packets for it. Tnx! 73 DE KB9QPM Ivy ... It's only an obsession.....only an obsession.....only an... -- ,-----> Ivy's WALL BBS Home of Lakeshore Net <-----, |---------------> Ivy Iverson, KB9QPM <--------------| `-> Netmail me a request for info on Lakeshore Net <-' ___ Blue Wave/QWK v2.20 [NR] --- TriToss (tm) 1.03 - (Unregistered) * Origin: Ivy's WALL BBS - Sheboygan, WI 920-457-9255 (1:154/170) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE300000 Date: 10/01/97 From: STEVE BRACK Time: 09:27pm \/To: IVY IVERSON (Read 0 times) Subj: Small AF Amps * In a message to Steve Brack on 09-30-97, IVY IVERSON said the following: II> SB> Well, Radio Shack's 277-1008 (for about $10) combines a II> SB> speaker & an amp that can be powered by 9VDC or from a $7 AC II> SB> adaptor. Almost every store stocks them. II> II> That's a complete amp, I was referring to a module. (I suppose one could II> gut one of the ones you mention and put it in a different case, though.) II> II> The amp I am referring to was a PC board about 1 1/2 X 3 inches, and you II> could feed a microphone into it, (I used small loudspeakers and output II> transformers connected in reverse), and it would put out a couple of II> watts - plenty to drive 4 speakers in different areas to reasonable II> volume in two buildings. (It was an all-call system which used the II> black-yellow pair in the phone wiring). Well, I haven't seen that item in my store. Sorry. II> But I guess RadShack doesn't think that people actually BUILD things any II> more! Of course, we do! In fact, there are more kits available now than ever before. Our Radio Shack Unlimited in-store catalog carries many kits of various levels of difficulty. II> I don't care to etch PC boards unless I have to, (it's messy and the II> chemicals are poisonous and I don't want my cats to get into it), but I II> would like to be able to pick up an occasional module, such as a small II> audio amp, and incorperate it into something I am building. (Heck, you II> can never have too many small AF amps lying around!) :-> True enough. 8-) My favorite (in-store) module right now is the IC voice record/playback module. I had a woman install one in her son's teddy bear. Now, every time he pushes its (nose?), mom tells him he's loved. Pretty neat, IMO. -- SPEED 2.00 #2712: (A)bort (R)etry (A)sk 12 Year Old? --- GEcho 1.00 * Origin: 9-1-1 FF's LEO's OSHA COMMS (619) 669-0385 (1:202/911) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE300001 Date: 10/02/97 From: JEFF EDMONSON Time: 11:06am \/To: IVY IVERSON (Read 0 times) Subj: High Gain Antennas for 2M > -=> On 09-29-97 13:14, Jeff Edmonson said to Ivy Iverson,<=- > -=>"About High Gain Antennas for 2M...,"<=- > JE> You see my message to Stan on Quagi's? Why not 4 J-poles (two riven, > JE> opposite of each other) two reflectors (same configuration) and yagi > JE> directors? Put the whole thing on a 20' wooden boom... > II> Nope, missed that one. Sounds interesting. > JE> It's been pointed out, it might be a bit cumbersome... but a pair of > JE> 5/8 elements as DEs and yagi directors does sound reminiscent of a > JE> Quagi. > II> Hmmm... Not quite what I had in mind, but it might be quite workable. > But a quagi is a quad loop, (possibly with 1 or more quad-type > reflectors), and one or more dipole-type directors, > isn't it? Or does it use dipole-type reflectors? A quad DE, quad reflector, yagi (dipole) directors. My point is, why not replace the quad elements with J-poles? > JE> for better front-to-back, it's been suggested (and even commercially > JE> sold) to add a reflector at the end of the boom, with a 50ohm resistor > JE> across the elements. A 'dummy-load' to signals from the back side f > JE> the beam, and at power levels on 2m such as most commonly 50w, it > JE> shouldn't be too hard to find or build a 50ohm load out of several w > JE> resistors in series/parallel for that power level. > Hmmm... so howcome I don't see it on beams or in advertising? Don't > bother answering that... ;-) > How much power would need to be dissipated? 10% of the transmitter > output? 50%? 50%, as I recall. Depends on the correlation between the reflector and the DE. if the reflector isn't doing the job as reflecting, it's probably absorbing some of the power generated by the DE. Might not be a bad idea to go with more. Would probably be best to go find a ceramic block resistor at the proper ratings. > My next question is, How much would this increase the > F/B ratio, and how would it effect the foreward ERP compared > to conventional reflectors? the F/B ration increases dramaticall. any signal comming in the 'back end' of the antenna is attenuated several db with the 'dummy load' reflector. There would be no change in the forward ERP gain. > And a stray thought: What would happen if you added > resistive loads to > the director(s)? Probably knock the foreward signal > down. similar to inserting a flow restrictor in a water hose ;-) 73 = Best Regards -Jeff KA5THB ka5thb@bigfoot.com --- FMail 1.02 * Origin: Electronic Avenue BBS 210-533-5668 San Antonio, TX (1:387/510) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE300002 Date: 10/02/97 From: JEFF EDMONSON Time: 11:08am \/To: ROB DENNIS (Read 0 times) Subj: TVI/RFI.... > Lucky for you! As of Sept. 30 we no longer have any cable TV here. [...] > The new TV antennas and amps are ordered and the arrive next > week and go up on their own support mast as soon as they get here. Cool. Let me know how that goes, as far as TVI is concerned. > JE>>> Remind them, if you're there, that Cable TV is supposed to > JE>>> be a 'closed-circuit' system, free from electrical > JE>>> interference. > Did so. > The smart-ass `supervisor's' response was for me to > stop transmitting on my `CB radio' and the TVI would > stop or take my radio to a `licenced technician' and > have the radio -fixed- properly. > I killed the CATV service right there by cutting the > feedline to the house and cancelling the service. > The look on his face was priceless. well worth it to, for their attitude. A slander suit comes to mind. 73 = Best Regards -Jeff KA5THB ka5thb@bigfoot.com --- FMail 1.02 * Origin: Electronic Avenue BBS 210-533-5668 San Antonio, TX (1:387/510) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE300003 Date: 10/02/97 From: JEFF EDMONSON Time: 11:10am \/To: ALL (Read 0 times) Subj: Thanks, Roy. (Thanks, Roy - great technical article!) 73 = Best Regards -Jeff KA5THB ka5thb@bigfoot.com 1st installment of the; Omni-Gain Vertical Collinear for VHF & UHF This is a rugged antenna, an omnidirectional collinear, which is capable of surviving some pretty harsh environments. It's an excellent choice for repeater installations and it can be easily top or side mounted to any tower. Bandwidth is normally 10MHz on the 70cm band and 25MHz on 23cm. Gain figures for this antenna are what you make of it. You can obtain approximately 3 to 10db over a dipole, depending on the number of elements you use. The main elements are constructed from 1/2-wavelength sections of coaxial cable. You can calculate the element length using the formula of; 5904/FMHz Velocity Factor of the coaxial cable you use. In my first attempt to build this antenna, I used RG-213 with a velocity factor of 0.66. You might want to use RG-11 for high power (250+ watts) or RG-6 for low power. To begin construction, remove the jacket and shield from each element and slide it into hobby brass tubing. You should select the diameter of the brass tube to just fit snugly over the dielectric of the coax. The brass tube provides more rigid support for each element and makes it easier to solder them together. (If brass tubing is unavailable, leave the shield and jacket of each element intact. Cut the shield to the formula length and remove enough of the jacket to allow soldering. 1/4" max) Use the above formula to calcualte the lengths of the brass tubes. I own a machine shop and can cut these tubes exact. By hand you'll have to get them s close as you can. At UHF and above, dimensions are critical to the overall performance and SWR. Cut the coax segment long enough to allow 1/16" of the dielectric and 3/8" of the center conductor to extend past each end of the tube. Make as many 1/ 2=wave elements as needed for the gain you desire: 4 elements = approx. 3.5 dBd gain 8 elements = approx. 6.0 dBd gain 18 elements = approx. 9.0 dBd gain 21 elements = approx. 10.0 dBd gain In addition, you will need a 1/4-wave element and a 1/4-wave whip for the top of the antenna. The whip is cut to a true one-quarter wavelength (no elocity factor correction) and is made out of number 12 wire or 1/8" brass rod. The next installment of the Omni-gain vertical collinear will begin the cutting and construction. Gather your materials now, and don't cut anything until you've read installment two. --- FMail 1.02 * Origin: Electronic Avenue BBS 210-533-5668 San Antonio, TX (1:387/510) --------------- FIDO MESSAGE AREA==> TOPIC: 188 HAM TECH Ref: EE300004 Date: 10/03/97 From: IVY IVERSON Time: 12:59am \/To: ROY WITT (Read 0 times) Subj: High Gain Antennas for 2M -=> On 10-01-97 08:22, Roy Witt said to Ivy Iverson,<=- -=>"About High Gain Antennas for 2M...,"<=- -=> 30 Sep 97 14:06, Ivy Iverson wrote to Roy Witt: RW> Hello Ivy. Hi, Roy; RW> o RW> / top view RW> o------o-------o-------o-------o------o RW> \ DE RW> o II> Ah yes, the good old corner reflector... Now if you were to II> replace the dipole elements with a 5/8 J-pole and suitably-sized II> elements, mount them vertically on a boom, (about 6-8 Ft long?), II> I wonder what ERP you would get with about 40 Watts at the II> antenna, (50W xmtr)? ... RW>> Build it correctly. Mount it behind the reflector...This is RW>> about a 7.5dbd antenna with a much better F/B ratio than you'll RW>> find in a normal Yagi. (Side view) | | | | | | | | | | | | | | _____|__|___||______||______||______||_____|| /\ R R DE D/\ D D D | | Mount behind or at CG? II> I'm sure! Are you talking 1/4 wave elements? If it's built with 6 dB II> J-poles, what would the gain be? How about adding more 5/8 elements II> to the J-poles? Hey, might as well dream big, right? RW> I've never liked j-poles, so you'll never convince me that such an RW> animal you discribe above should exist. It's nice to experiment with RW> antennas, but this has got to be a nightmare... Heh heh... Howeverf it WOULD be, to me, an interesting experiment. II> And if you have a 6-8 Ft boom, that would be quite a strain to mount II> it from behind. I think it would be more effective to mount it at II> the center of balance, on top of the supporting mast. RW> You still mount it from behind and use a counter-balance to compensate RW> for the overhang. I did this for a local cable provider who couldn't RW> recieve a certain FM station without interference. I built them a yagi RW> designed for the frequency of the station and mounted it from the rear RW> with a counter-balance. A 5 element yagi for 97-100MHz... There is another way to this, as I learned when I was on the engineering staff of a University station in Iowa: Two cut-to-frequency yagis, one mounted 1/2 wave in front of the other, and connected with a 1/2 (or 3/4) wave harness. The rear antenna feeds the receiver. (I think I remember this correctly). The F/B ratio is almost comeplete, as is the side rejection: R DE D D o--o--o--o To RX-/ |\ ========|==\==| \| o--o--o--o R DE D D II> Do you REALLY want a 2M "cannon"? RW> Nope. I work UHF, exclusively. AH. No HF either? II> Have the J-poles paired, above AND below the mast! II> Also, what difference would it make if the corner had a screen II> instead of duned reflectors? RW> RW> tuned? round? ?? Rectangular... a classic V-shaped "corner." RW> The screen will give you a higher F/B ratio. II> This would require a non-metallic mast unless it were rear- II> mounted, but if the DE's were properly phased and everything II> optimized (resistors in the directors, etc?). RW> Why would it require a non-metallic mast? Because of the J-pole? If the J-poles were vertically arranged both above and below the boom... II> .. That just MIGHT be hot enough for moonbounce if it were mounted II> on AZ-EL rotors! II> (It would also be about 15 Ft high and quite heavy with a lot of wind II> resistance!) RW> And more trouble than it's worth...:) Perhaps... but fun (for me) to contimplate... and it could be scaled for any higher frequency. 73 DE KB9QPM Ivy ... Double your dipoles. Double your flux. -- ,-----> Ivy's WALL BBS Home of Lakeshore Net <-----, |---------------> Ivy Iverson, KB9QPM <--------------| `-> Netmail me a request for info on Lakeshore Net <-' ___ Blue Wave/QWK v2.20 [NR] --- TriToss (tm) 1.03 - (Unregistered) * Origin: Ivy's WALL BBS - Sheboygan, WI 920-457-9255 (1:154/170)