Does anyone use 70cm transverters for FM Repeaters?

Roy Laufer

I don't operate on the low frequency end "weak signal" side of the 70cm band, but I do use 70cm Repeaters and I really like seeing activity on the whole band on a SSDR panadapter. Now that I have the ThumbDV I thought it would be nice to try it out on 70cm D-Star Repeaters.

So, I went looking for a 70cm transverter, but all that I could find were "weak signal" frequency ranges, not the Repeater band. I found a manufacturer who suggested that they could "relax" their filters to broaden their range, but instead of 60 watts output, all I could get were 3-4 watts, and the pre-amp had a negligible gain. I contacted the company and they offered to retest the transverter and see what could be done. In the end they decided "loosening the filters" would not be sufficient. I would need a model built using custom filters. They will start assembling it later this week, and I should have it to test by the next week...

My question is: Am I the only guy that wants a transverter for Repeater use? I realize it's a bit overkill for Repeaters, but I've read of stranger ways of over engineering a solution to a problem by others.

I'm guessing there is little to no demand for such a product?

73,
Roy AC2GS

David

You're not alone. I would like to have an all in one solution of 160-440. I have a 144 and 220 from transverter-store.com and was looking for 440 to round it out but like you discovered none cover the repeater part of the band. It would also be great to be able to have support the XVTR and HF so you could monitor a local repeater and work the HF bands and visa-a-versa. Unfortunately it is seems adding VHF and UHF support even at low power is much more costly and not something FlexRadio is interested in doing and understandably.

I'll be interested in your 440 solution.

Roy Laufer

I can understand why FRS wouldn't be that interested in the relatively small number of people willing to spend more $$$ on this feature, but it seems strange to me that no one has a transverter version for this portion of the 70cm range (maybe my effort will start a trend<g>).

I'll let everyone know how this works out.

Mark Gottlieb

I am looking at a DownEast Microwave 70cm transverter L432-28 which puts out 60w.  My only access to DStar, in my area, is on 70cm.
Roy- Is the manufacturer you are talking to DownEast Microwave?  It would save me a lot of money if theirs is not applicable for DStar repeaters.

Mark
WA2DIY

George Fenwick

Transverter store now has a 440 xvtr.  I believe it covers the entire band.  Not much front end filtering . .   And the Flex 6300 32 mw most likely will not drive it to its rated (~3-5) output . . 

George W2AIV

David

I have talked with Serge at transverters-store about the 440 and he confirmed it does not cover the full 440 band. The issue is the crystal they need to get the repeater portion of the band (442-450) is not available to them.

RF range  -  432 ... 442 MHz
http://www.transverters-store.com/432mhz.htm

David

Looking at the PDF the standard for that unit is  432 MHz, 432-28  (432-434 MHz). DownEast Microwave will do custom builds and may be able to make a unit in the repeater range though the repeater range is wider than the 2MHZ of this unit shows. Best to call them and discuss the options.

Mark Gottlieb

You are correct.  I just noticed that. It would not be applicable as advertised since my DStar repeater is 440 MHz locally.

thanks for the heads up.

Mark
WA2DIY

Roy Laufer

Yup, I'm talking about Downeast Microwave. Again, I know of NO standard 70cm transverter that is designed for the Repeater portion of the 70cm FM Repeater band. Even DEMI does not have these as simple options.

They had to special order components (I assumed it was filter components) to obtain the proper upper range, which might add an additional delay. I initially ordered my transverter in February, so I'm talking about some serious time in my case. I was glad that they offered to build me a custom box for my purposes.

I doubt that the lower frequency range will be very useable - so this is not a solution if you really want to work the lower weak signal range with the same transverter - the 70cm band is just too wide for present transverters.

I would suggest that you give me a week or two. By then they assure me that the custom box will be assembled and shipped. At that point I can tell you how this experiment worked out.

Then, maybe you could ask for the "AC2GS model" <HI HI>.

Mark Gottlieb

Just spoke with Downeast and they will modify the transverter to cover the 70cm repeater portion of the band.  I asked for a quote for 439 MHz to 449MHz.  I will be holding on to the desk wth both hands when I get that price.  But, they can modify the unit for FM, as they claim, which will eliminate the SSB capability of the unit.

Mark
WA2DIY

Mark Gottlieb

Roy,

Also, correct about there being nothing on the market applicable for standard 70cm FM repeaters.  Elecraft will not go there either.  The transverter store, as previously mentioned, does not have a 28 MHz IF transverter for 70cm.  It is driven by 27 MHz IF which, of course, is no go.   He has e-mailed me saying that they will have a 28MHz unit available in a month.

Mark
WA2DIY

Roy Laufer

I may be mistaken, but I don't believe that the custom box is not capable of SSB operation, but that it is outside the SSB band plan - six of one, half a dozen of the other. The additional cost shouldn't cause any high blood pressure episodes, unless they have found another solution than mine.

I'll let you know how well DEMI's custom job works.

Mark Gottlieb

I was onlly repeating what the young lady had said regarding the unit's capabalities once it was modified to my specs.   I really will not regret the loss of SSB if that is the case anyway.  Not much DX on 70cm sideband last time I checked the cluster.  Hi Hi  

I will post my results when I get the unit.   If the waiting time is accurate for this, as posted, it looks like I will be ringing in the New Year on 70cm.

Roy Laufer

I believe that DEMI usually quotes 3-5 months from order to shipping. It appears to be a small business that assembles units, one at a time, with a large collection of orders already in the queue. Some components may be special orders, and that may introduce an additional delay.

I hope that you will be able to ring in the New Year on 70cm, but it might take an additional month or two beyond that point.

Good luck!

Ham Radio can be "a waiting game" - I've been on Larry Phipp's LP-500 Digital Station Monitor waiting list for four years...

Justin - KL2D

I was planning on doing the same, using a transverter for local FM work since the flex is currently the only radio left in the shack. I was going to use the Elecraft but hadn't looked closely enough at the specs... glad to see I'm not the only one interested in this. If I manage to find a solution I will post it here... or hopefully someone smarter than me will find it first <g> 

k3Tim

Same here, was going to use a xvrtr for 440Mc in the repeater portion.  Sure glad I saw this thread.  

_..--
k3Tim

Corey/ KC0YNS

I'm also in that same boat, I'll be watching what information is passed down.  So Are the Spec's on the 2 meter transverter the same way? FM only or will they also do SSB?  I'm not to the point of buying either now but will be in a month or two.  

Roy Laufer

The problem (as I see it) is that transverters seem to be engineered for a 2 MHz bandwidth to fit the 28 MHz IF drive signal. The demand seems, historically, to be in the lower end "weak signal" SSB end. The 6700 can use the DEMI 2MLDPA, which takes a 2 meter receive/transmit XVTR signal and applies a low noise pre-amp/linear amp, which maintains the full 4 MHz. bandwidth. Normal transverters seem to only work the lower 2MHz end. 70cm transverters also focus on the 432-434MHz weak signal SSB band, rather than the higher end FM Repeater portion. I will be testing out a custom DEMI transverter designed for the 435-450MHz FM Repeater range.

Again, to my knowledge, there is no limitation in the custom design that disallows SSB transmission - it is a matter of what modulation modes are allowed with the present voluntary band plan.

I will let everyone know how I find the 70cm transverter custom filter design. 

Mark Gottlieb

Ok.  Finally got my quote for DownEast microwave FM mod of their transverter.  For the 50W version, FM only, the charge is $699 + shipping.  For the 25W version, FM only, the charge is $524 + shipping.  Both of these mods will give me access from 439MHz to 450MHz output to access FM and DStar repeaters in my local area.  Now I have one more question, just to make sure, before I push the credit card button...With this FM output + ThumDV + SmartSDR DStar utility, will I have access to my local 70cm DStar repeater or am I missing something else here?  Thank-you.

Roy Laufer

Once again, I do not believe that the custom mod affects the amplifier's linearity, which would be the only reason that it would not be unsuitable for SSB. Rather, I think the selected new band pass filters are in the higher range where the band plan does not allow for SSB transmission.

Nevertheless, D-Star implements a modulation technology called Gaussian Minimum Shift Keying (GMSK) which has a constant amplitude just like good olde FM, and is insensitive to amplifier nonlinearity, so it should work.

You might ask Downeast Microwave, or you can ask me in a few weeks when I get model #0001 and try it out with my ThumbDV.

Nothing's going to happen at DEMI in the next few weeks other than having your name placed at the bottom of a very long list of orders, so I assume if my unit doesn't make the grade they will cancel your order (they don't bill until the "build time").

Good luck!

As always, your mileage might vary.

Tim - W4TME

Now I have one more question, just to make sure, before I push the credit card button...With this FM output + ThumDV + SmartSDR DStar utility, will I have access to my local 70cm DStar repeater or am I missing something else here? 

The D-STAR implementation in SmartSDR works in both simplex and repeater mode. 

Mark Gottlieb

Roy,

Did you order a simlar mod from DEMI?  I guess you have both answered my question.  I was only making sure that the FM output on the transverter will be "converted" to a DStar signal using the ThumbDV and SmartSDR DStar implentation on the FLEX 6300.  When I talked to DownEast, I did not get the sense that they were knowledgeable about this which is why I put it to the group.  I think the horse has been beaten enough.

Thanks everyone, I am going all in.

Mark
WA2DIY

Roy Laufer

Yup! My guess is that after they build mine (and test it???) then they'll use this design for those Repeater fans that come after me...

This will be their second attempt (but I think the first one was not that too enthusiastic, nor aggressive - they probably just eliminated some of the higher order filter stages).

My guess is that they have little to no experience with digital technology, their experience seems very much analog, so I can see that they did not want to be too specific.

I asked them about the chance of using their transverter with DMR, but since it uses Time Division Multiple Access (TDMA) and requires the keying of the transmitter at 30 msec duration packets, DEMI's relay operated devices will not be useable (if a transverter had a pin diode switching circuit TDMA might be "doable"). 

The best solution is to stay tuned to this forum when I review "the AC2GS Model".

Perhaps we will have a QSO on a linked D-Star Repeater using our Flex's someday.

Good luck to us all!

[Consider the dead horse beaten back to life and dead again - may PITA forgive me]...

Roy AC2GS

David

Mark, who at transverters-store said they would have a 28Mhz (442-450 coverage) in a month? I was talking with Serge and he said the current unit could do up to 450 if the radio can tune to 38Mhz for 442 as an example and so on. I know that I found the 220 unit was able to do RX/TX 195-268Mhz using the Flex 6000 XVTR. They are working on another design of the high performance 432mhz board with more output power (~10W) and high ip3 which can be used even in EME operation. The higher would be good since the Flex has a max of 15dBm and the transverters-store use 20dBm for max drive. For my use their boards are a cost effective option not perfect rock solid but get you on repeaters and provide a nice panadapter view of those bands.

Ideally it would nice to 144, 220, and 440 built into the Flex with 5-10Watts or an easy add-on that would permit using those bands at the same time as the HF which isn't possible with the transverter from my experience, but this is just a wish.

Roy Laufer

For what it is worth with two hardware receivers you can have two transverters showing their band's spectrum, but only one band will transmit.

I've done it. Having UHF, VHF AND HF would be fun, but that would require a radio with THREE hardware receivers (and some people think that 8 virtual slices might be too much of a good thing).

FRS could have built their 6000 series with electronic back scratchers, but you just have to draw a limit on any design...

Mark Gottlieb

It was on eBay and I was asking questions about eBay item number:
221879675010.  This transverter has an IF of 27MHz and I was looking for one with an IF of 28MHz.  Here is the quote:

Dear fletcher885,

We are going to get the new version of the 432mhz transceiver within a month or so . It would work on 432/28mhz. But it is more complicated board with high performance and it costs 50 USD more. 
Anyway you can use buy now option and buy the 144mhz transverter or kit and I send you back 10 USD as a discount. Thanks 

- transverters-store

AA0KM

I am wondering and waiting if  someone would build a VHF/UHF SDR all-mode radio.

Been searching some but not finding much.

Mark Gottlieb

Of course there is the UDRX-440 by NW Digital but it is only 70cm whiich is still in development but appears to be the most promising candidate for SDR  Linux platform.