We have had great luck with Heliax duplexers also, with four in service. Easy to make and cheap.
--- In [email protected], "Mike Perryman K5JMP" <[EMAIL PROTECTED]> wrote: > > Skipp025 ->>"Something you did in your project was not as well done as it > probably could have been." > > > I am running a heliax duplexer, and it has seen 100° to 15°... no issues so > far. Skipp knows all the details... and there is no majic. > > Perhaps you need to take another look at construction technique.... > besides, if it is all copper, then the expansion coeffeicient is constant > throughout... no? If that is the case, then the relationships do not > vary... so where is the issue? > > IMO the biggest issue with a heliax duplexer is mechanical stability... due > to bumping, banging, etc... not thermal expansion or growth. I can build > them all day long... but if I could find a way to ship them, and have them > arrive "in-tune" I could make a fortune... God knows I am trying.. LOL! > Working on that one... just not willing to release the info 'til I KNOW it > will be rock solid in shipping.. Yes, I have built and shipped several to > another individual I trust, and the curret design just isn't stable. > > I took a shot at building my own "cans", but without the proper goodies to > machine the descreet parts, it was a waste of time. And without > silverplating everything, you will not acheive commercial specs. The "Q" of > the circuit is everything. While I don't have a lathe, others have > contributed time and resources to forward the heliax design. It is a very > valid concept, I just need to iron-out implementation. > > I will say it again to reinforce the thought... it is a very valid concept, > don't write it off. > > Right now I am kinda soured on radio due to neanderthals in my local > environment... so of late I have been concentrating on drag racing.<-- this > IS my first love...< Radio doesn't compare to the rush I get covering 1300 > ft in 9 seconds... heh! Then get to drive the same car to work on Monday > morning... woot! > woot![IMG]http://deephousepage.com/smilies/bananalama.gif[/IMG] > > Contest when the oppurtunity presents itsself, and building thumpin' small > blocks (or pig-blocks --->gag!) for the primary hobby. 630hp from a > smallblock on pumpgas, now add 300hp of NO2... got wood yet? Yeah, it can > be done... almost 2 hp per cube plus NOS... requires that you keep your > head in the game. It sits in my backyard as we speak, 630 hp& 570 ft/lbs > torque from a 355ci smallblock on pump gas, all N-A motor... no chemical > reactions, hair-dryers etc... play chemistry and things get interesting. > It gets close to 1000hp.... get the picture? > > Chemistry requires a lot of math, or a lot of money... your choice... so > does a filter. > > Wanna have some fun... how about 1800hp from a small-block. A guy gave me > a blank check and said make it really fast. Big freakin' turbo... So far we > have only been able to put about 1100 to the track, yes there is a ton of > computer mgmt going on here.... and it still leaves a lot of room for > improvement.... but he is running 6.70's in the quarter with a > door-slammer. > > The same can be said for the heliax duplexer. Works good, but it could be > so much better! > > If you don't get serious, you won't realize the benefits. Decimal points > count... what more can I say? > > If I can do all that, surely any of you can build a series resonant notch > filter.... it really isn't that tough guys... there is no majic. You can > do this... > Apply yourself, and your talents before you write a design off... > > My final answer... > > Precision counts. Without the ability (the mindset required) to adhere to > the physical relationships... you are wasting your time... might as well > break out the credit card and whine a bunch. Most folks do exactly that.. > if you can't afford commercial cavities, you best sharpen your pencil and > get your calculator out.. time is a wastin'. > > Serious engineering requires serious disclipline... don't deviate from the > laws of physics or you will get your ass kicked. This ain't HF... > > 'nuf said. > Just my [IMG]http://deephousepage.com/smilies/twocents.gif[/IMG] and it is > 3:03 in the morning... need to sleep... later.. > 73 > Mike > K5JMP > www.k5jmp.us > > > -----Original Message----- > From: [email protected] > [mailto:[EMAIL PROTECTED] Behalf Of skipp025 > Sent: Monday, December 25, 2006 9:21 PM > To: [email protected] > Subject: [Repeater-Builder] Re: 6M cans made from other metals > > > > "" <pulsarxp@> wrote: > > I have built cans in the past and would NEVER do it again. It > > is a waste of time. > > Some people don't have great results... > > > As the metals expand and contract, so does the tuning. The > > main tuning rod shafts are the biggest problem. The metal > > needs to have ZERO coefficient of expansion properties. Unless > > you have access to such material, DON'T GO THERE! > > I went there with pretty good results... if you build the > plungers right you don't have a big problem with drift once > they're locked down. Telewave's plungers are just copper > pipe with quality fingerstock. You don't have to use metal > threaded rod... > > > I had to tune the cavities I made around 7 times a day in > > a relatively stable but not totally stable temperature > > atmosphere. > > Something you did in your project was not as well done as it > probably could have been. > > > Yes, it is a very good learning experience so you can > > appreciate how good a commercial set really are. > > Probably true in your example. > > > The can changes can be minimized by making use of a VERY LARGE > > diameter can, such as a metal garbage can, so its change has > > little effect on the center section. > > Not the way to go about things... more like material thickness > and rigidity are the big players in the game you mention above. > These stove pipe cavities I have here include steel angle iron > bracing on the cavity hot end. Decades of stable operation so far... > > > ZERO coefficient of expansion metal is vital. I can assure > > you, you will never be happy with a home made duplexer. > > opps... now I've got to go pull the 5 or 6 home brew duplexers > we use out of service. > > cheers, > s. > > > > > > > Yahoo! Groups Links >
