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1-7 of 7 messages
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Transverters! How good are they?
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by N2RRA on December 9, 2004
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How much better are transverters than a stock rig?
I have heard the reciever end are better as the transmit the same. Would you say takeing a 144Mhz transverter and hooking it up to a lets say 756 would out perform a 746/746pro on 2meters or even some of the more nortorious 2meter monobanders?
Will some of the functions still work for example the 756 band scope?
What exactly would be the benifits of a high priced transverter besides eleiminating a big rig to make more space?
Thanks,
Eric
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RE: Transverters! How good are they?
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by K5LXP on December 10, 2004
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> How much better are transverters than
> a stock rig?
Depends on the transverters and rigs you're comparing. Since it's basically a receiver front end and 1st mixer, attributes such as RF selectivity and gain are important, along with dynamic range. These should be specified with the transverter. The 'real' selectivity is in the IF radio, so it's performance along those lines will also impact overall how well the transverter performs as well.
> Would you say takeing a 144Mhz transverter
> and hooking it up to a lets say 756 would
> out perform a 746/746pro on 2meters
You would have to evaluate the units together as a system, then compare the spec's. Having owned both an ARR receive converter (for satellites) and an Icom 746Pro the 746 was a better performer in terms of out of band rejection. I don't have the facilities to measure actual selectivity, dynamic range and IP3 but I know the ARR got 'crunched' more than the stock 746 does. You should check the ARRL website, I recall that they've done lab testing on a few of the available transverters out there. "Better" is relative, since on 2M you don't usually operate in contest conditions and even marginal specifications will usually work OK unless you're looking for the
utmost in weak signal performance (EME, meteor scatter, etc).
> Will some of the functions still work
> for example the 756 band scope?
That is an IF function, so yes.
> What exactly would be the benifits of a
> high priced transverter besides
> eleiminating a big rig to make more space?
You may not be eliminating anything, or even adding more depending on the combination you choose. You can pretty much plan on adding a power amplifier, since most transverters don't put out high power. This would be important for weak signal modes, and sometimes satellites. It would need to be linear, not just an FM 'brick'. You would need to drive the transverter at a proper level (low power), which may take some tricks unless the rig has a transverter port. It would also need a power source of some kind. So you'd end up with at least two somewhat expensive boxes hanging off the back of the HF rig with a few steps to switch from HF to transverter operation. Contrast this with the cost of buying an off the shelf rig capable of the band you wish to operate that requires no external equipment.
Mark K5LXP
Albuquerque, NM
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RE: Transverters! How good are they?
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by N2RRA on December 10, 2004
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Hi Mark,
Thank you very much for the great response. I think you sum'ed it up quite well unless anyone does'nt agree. Sounds about right according to my own theory.
I will check the ARRL websight for more info and see what i plan on doing.
Great break down!
73,
Eric
N2RRA
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RE: Transverters! How good are they?
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by WB2WIK on December 10, 2004
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ARR doesn't make transverters, so I assume Mark was referring to a RX converter (only), which they do make -- and good ones.
"Transverters" are both RX and TX, of course. Some of the really good ones are excellent and do seem to consistently outperform stock transceivers, mostly because they contain so much specialized single-band circuitry that can add RF selectivity in both directions. (Not *IF* selectivity, which of course is found in the baseband rig.)
Best I've used are SSB Electronic LTxS series (made in Germany). They make transverters for 50, 144, 432, 903, 1296 MHz and I think 2304 MHz also. Don't think they make a 222 MHz model. When Microwave Modules LTD was in business selling amateur transverters back in the 70's and 80's, many of their products were excellent, also. My MMT50/28S was probably the best-performing 6m "rig" I've ever owned, connected to a TS-830S as a TX/RX IF. Damned thing could hear a pin drop on a very crowded band, and easily kept pace with my 4-1000, 1500W PEP output linear amplifier. If anybody heard me, I heard them.
Down East Microwave in NJ makes a complete line of VHF-UHF-SHF-EHF transverters from low VHF through 10 GHz and they're pretty good and affordably priced.
One big advantage to the "transverter" route is when you use them for multiple bands with a single baseband transceiver, such as your 756PRO with a stack of transverters to cover several bands. All you need's a multi-position coax switch and you can wire them up for instant bandchanging, which can be an essential activity in a VHF contest, for example. And with a single baseband rig, as you change VHF-UHF bands, you stay (relatively) on the same frequency in the band, so it's easy to go from 144.2 to 222.2, to 432.2, to 903.2, to 1296.2, to 2304.2, etc. just by clicking a switch. Tell the other station, "Meet you one band up, same frequency," and boom -- you're there. This is how VHF contests are won.
I don't know what problem Mark (K5LXP) had with the ARR receiving converter, but I've used several models for several years and think they are superb; however, they do have WAY too much gain from RF to IF (conversion gain) which can easily overload baseband HF rigs. I just turn the gain down (a lot) or use a 20 dB attenuator on the front end of the HF rig to deal with that, and this greatly increases RX dynamic range.
WB2WIK/6
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RE: Transverters! How good are they?
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by K5LXP on December 10, 2004
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> One big advantage to the "transverter" route is
> when you use them for multiple bands with a single
> baseband transceiver,
I considered this somewhat of a liability in terms of cost and operating convenience. When I added up what it would cost to assemble even a modest 2M/440 weak signal setup using transverters, amps and plumbing it was almost as expensive as the 910H I ended up with. Transverters only work one band at a time, I wanted to work duplex for satellite. Yes, I could've run a separate HF+transverter for the other band but it didn't seem practical to have all that gear tied up for what one box can do for about the same cost. Each band requires a transverter and an amp, which gets spendy after the first band. It could probably be demonstrated that one particular model/brand or another of transverter could outperform the 910 in some respects but having everything in one box, computer controlled, full duplex, high power, etc kind of outweighs a few dB here or there in the spec's.
> I don't know what problem Mark (K5LXP) had with the
> ARR receiving converter,
Probably unique to my location, but I was getting hammered with 150-160MHz crud. Same problem with my IC706 on 2M, but not a problem with the 746 or 910. I probably could've put a helical or stub filter on it but a receive converter wasn't fitting into my station plan in terms of # of boxes versus utility. It did seem plenty hot but that's kind of lost when the paging tones and grunge come through.
Mark K5LXP
Albuquerque, NM
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RE: Transverters! How good are they?
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by WB2WIK on December 10, 2004
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Hi Mark,
Yep, it's easy to see how different setups are "best" for different people, and maybe even different environments.
The transverter + HF rig setup is more for contesting than for satellite work, and for a S/M (single op, multi-band) contest, to be competitive you need *lots* of bands, not just 144-432-1296 like the IC-910H can provide. The typical "rover" station around here, and many back east also, are "ten band" rovers, set up for 50 MHz through 10 GHz. Without stacked up transverters, nobody'd ever be able to pull that off, especially in a car or light truck!
I still have (and like) my old FT-736R. It's set up for four bands, 50-144-220-432 and besides being a good rig, it is satellite worthy and can cross-band duplex. I'll probably keep it until it blows up, and maybe a while after that. :-)
WB2WIK/6
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RE: Transverters! How good are they?
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by N9DG on December 20, 2004
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As others already pointed out they can only perform as good as the HF radio that you use for the IF. At the outset you will not save money by using transverters to get on the so-called weak signal parts of the VHF bands. The multi bands in one box radios will get you on several bands for less. Where economics start to shift into the favor of the transverter approach is when you decide to have continuous *and* simultaneous coverage of all 4 bands from 50 - 432 MHz. If you really want to be able to continuously watch the 50 and 144 MHz bands for each and every little DX band opening that there may be this capability is essential. With the all bands in one box radios you are looking at a sizeable chunk of money to do this since none of them allow for more than one, maybe two bands of simultaneous RX. In this case a few decent transverters and modestly priced IF radios for each of those bands will get you more capability for less money.
Additionally if you want to use spectrum sweep displays for all of the V/UHF weak signal bands you must also use a transverter since no commercially available ham V/UHF radio can provide that today. The Icom IC-746 will only give you 50 or 144 MHz, not both simultaneously; and the Yaesu offerings for VHF+ have no spectrum sweep whatsoever. Once you've used a spectrum sweep on V/UHF during a contest or a band opening you will probably feel that not having it is like wearing blinders.
In my case I started out with the typical V/UHF multimode for 50, 144, and 432 MHz, I then added a 222 MHz transverter coupled to an older non-synthesized (low phase noise) HF IF radio. What I quickly discovered was that the 222 MHz system outperformed the other two bands handily, signals would just "stand out" from the background noise. At that point I then decided to convert entirely to transverters for all my V/UHF bands. I have no regrets in having done so. About that same time I discovered the power of spectrum sweep displays and point and click tuning by using a Ten Tec Pegasus and N4PY software. The Pegasus is however only a mid-range performer in terms of dynamic range but its spectrum sweep functionality has clearly proven its worth in spades here and mostly offsets its other shortcomings. And when a newer and better performing (but still economical) radio comes along in the future I will only need to swap out the herd of Pegasus HF IF radios; the transverters (and power amps) will not likely need to be changed at all.
If you do pursue the transverter route I would stick to Down East Microwave (of *recent* vintage), SSB Electronic, or Elecraft. These three brands of transverters all use high level mixers for high third order intercept and IMD dynamic range performance. They will outperform the HF IF radio that is attached to them in most cases with the exception of the "top of the line" performing HF radios out there. Most of the other older transverters will indeed get you on the bands but they aren't always very good if you want to get into VHF contesting though. Don't even consider the 60's-70's tube based transverters at all for a number of reasons.
And finally the key thing to look for after third order intercept performance is Noise Figure (NF); for 144 MHz and up look for a specification of less than 1dB for NF, for 50 MHz a 1dB spec is ok. Don't be over concerned about gain though, most transverters have plenty of that. In fact you will find for the best performance you will want to manage the transverter’s gain to be "just enough" to overcome mixer and other losses within the transverter. With a low NF front end transverter you should hear a "just perceptible" rise in band noise as the transverter is turned on (no antenna on the input). Anything more than that you will degrade the overall IF radio/transverter system dynamic range.
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