JUMA views & prospects

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JUMA views & prospects

Postby DL3BBW » 24 Jan 2013 21:01

I am more or less ready to get the JUMA TRX2 + JUMA PA100-D.

Sometimes it takes a while to propose questions as good as
possible. I thought about the JUMA products many times. Then I put it
back again into the area "later, later"

Now finally I would like to brainstorm my questions for once and for good.

Additionally I have some more questions who are not mine, because their
is another amateur interested in JUMA products here close by. My friend
didn't even knew, that products like yours exists.

* There are 3 Filter positions possible!

1. Are those 3 Filter positions for SSB AND 3 Filter positions for CW OR
3 Filter positions for all modulations?

2. How many Filter positions are available for the Transmitter? Either

3. Can the available filtering bandwidth both for reception AND
transmisson customized free (just for me; At least innitial one time)?

4. Is it possible to customize to transmission bandwidth for SSB as
followed: NAR=[low cut 300 Hz; High cut 2700 Hz (2.4 KHz bandwidth)],
MID=[low cut 200Hz; High cut 2.900Hz (2.7 KHz bandwidth)], WID=[low cut
100Hz; High cut 3.100Hz (3.0 KHz bandwidth)]. Is that possible?

5. For reception I wish for instance following values in SSB: NAR=[low
cut 200Hz; High cut 3.000 KHz (2.800 Hz bandwidth)], MID=[low cut 100
Hz; High cut 3.400 Hz (3.300 Hz bandwidth)], WID=[low cut 50 Hz; High
cut 4.550 Hz (4.500 Hz bandwidth)]. Cauld that be maintained?

6. Can the MIC-Input be adjusted for the use of Dynamic microphones?

7. Do you have a MIC gain in the machine (I didn't saw it).

8. Can the compression level be adjusted at any time?

9. Is a microphone equalizer available in the radio.

10. I want to use additional to the JUMA amplifier another one as well,
so I need the TR/TX line for that amplifire. And I need approx. 140W out
of the JUMA PA100-D in order to run full output with my second
amplifier. Is that possible?


Questions from my friend

to juma trx:

1 - when is 600m available

2 - diversity receiption. 1 juma must as master control the other
n-juma´s on exactly same frequency, <1Hz. Is that possible? I want to
get out the I/Q-Signals and fed them into modified PowerSdr-Software (or
other). AND i can change the directions per hardware (1 vert per 1 juma
+ feeding/phase-lines). => Hardware PLUS Software-Decoding. Should be
better than every rig you can buy.


I've been asked what my application will be¿?

Well? I want to run the JUMA TRX2 as my only main radio here in Germany.
And I can tell, that I will be heard. So it is very very important to
produce clean, clean audio. I want to use a Heil PR40 microphone
together with the JUMA TRX2

Why those strange sounding bandwidth? 4.500 Hz in SSB? Why? Well, when I
tend to listen shortwave radion I like to have it wide. To narrow a
signal is no problem with external equipment. To make it wider is

And last not least I DON'T LIKE those big huge boasting radios from ICOM
type IC 7.600.

I like to have it small and neat. The ICOM IC-7000 isn't as good as I
wish. The New ICOM IS-7100 looks to me like an alarm clock. It might be
a good item, but I would get all the time angry how it looks like; So?
Just therefore I cannot buy it; I know me! So? What choices I have? Not
many. Actually the JUMA TRX2 is the only radio, which is left of interest
(according to the size).

It may be considered for the future to add more features to this fine
appearing rig.

73 de Hans-Heinrich - DL3BBW
Posts: 1
Joined: 24 Jan 2013 20:10
Location: Germany

Re: JUMA views & prospects

Postby 5B4AIY » 28 Jan 2013 11:08

OK, let's try and answer some of your questions.
The Juma has three receive filters available, Narrow, medium, and Wide. The bandwidths of these receive filters are user configurable both in the original firmware, as well as in my modified firmware.

There is a single transmit filter whose bandwidth is fixed in the original firmware, but if you install my modified firmware, then this filter's band width is also adjustable.

The CW facility does not require a transmit filter, the carrier is directly generated from the Direct Digital Synthesiser, remember, this is a direct-conversion transceiver, there is no intermediate frequency signal processing as such, unless you consider audio to be the IF.

The low frequency cut-off of all the receive and transmit filters is fixed, no adjustment is available, it is determined by the hardware components. Of course, if you wish, you could alter these to suit your own preference, but making the low-frequency cut-off adjustable would be quite a 'savage' hardware operation, and I would not reccomend it.

As for having customised high-frequency cut-off limits, this is possible, and in my modified firmware if you wished to have different cut-off frequencies, it is only a matter of 'changing the numbers'. If you are up to it, you could modify the firmware yourself, and you are welcome to my source files if you wish. Alternatively, speak to me nicely, and I might even give you a 'special' version with your upper cut-off frequencies, it's not a real problem.

The transceiver has as a rear-panel output a T/R line that can be used to key an external amplifier. It is not required with the companion PA-100D linear as this is handled by the Juma hardware directly. There appears on the Juma RF output connector a DC voltage that is used by the PA-100D to switch it into transmit, so no additional T/R conection is needed. This buffered voltage could also be used by you. Have a look at the schematics for further details.

The MIC input is primarily intended for an electret condensor microphone, and thus has a bias voltage. However by placing a 2uF capacitor in series with the output from a dynamic mike, then you could use one as well. I have done so perfectly satisfactorily. In my case I was able to place the capacitor inside the mike case. Most dynamic mikes have a somewhat lower output than a condensor, and so the SSB gain needs to be increased. But to answer your other question, yes there is a microphone gain adjustment on the main board. If you intend to use a digital mode, then the input needs to be switched to the LINE input sensitivity.

There is no equaliser in the radio. If you want to customise the frequency response, then you will have to use an external equaliser. The microphone compression level is not adjustable, it is only a simple peak clipper. I use an external compressor, in this case one from your fellow countryman, Joachim Munk, DF4Z. This is a RF compressor and can be fitted inside many microphones. As it uses power, and this is not available from the Juma, you would have to provide an external power to the mike.

Finally as for the Juma PA-100D, it is conservatively rated at 100W, but in fact is capable of somewhat more than this. If you are only going to use SSB, then you should be able to get about 140W from the PA-100D, but it will run somewhat warm. If you want to use CW/RTTY/PSK31, then as with other amplifiers, you will need to reduce the drive level and run at 50W.

Hope this is of help.
73, Adrian, 5B4AIY
Posts: 188
Joined: 13 Nov 2011 09:22
Location: Cyprus

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