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JUMA Kits Availability

Good news to all,

The most popular Juma kits will be available soon. The new supplier Yrjo OH3YP has been working hard. The first kits will be available soon, keep watching Juma Shop.

73 Matti OH7SV
by OH7SV
27 Mar 2014 18:04
 
Forum: Juma Discussion
Topic: JUMA Kits Availability
Replies: 3
Views: 3774

Re: TX500 tx output, Missing signal Pin 76

Alex,

If the CW keyer is working and TX500 is in TX state the processor pin 76 should be going high/low as keying signal.
Is the CW keyer working?

73 Matti OH7SV
by OH7SV
25 Jan 2013 08:31
 
Forum: Juma Discussion
Topic: TX500 tx output, Missing signal Pin 76
Replies: 2
Views: 2852

Re: TRX1 PA Board

Marc,

The 2.5k high value is ok because there are 3 trimmers and other components in parallel.

Pse check your ohmmeter by shorting the meter wires. It should show zero to few ohms. If you have got a low ohmic resistor e.g. 100 ohms, test your ohmmeter with that too.

73 Matti OH7SV
by OH7SV
23 Nov 2012 07:16
 
Forum: Juma Discussion
Topic: TRX1 PA Board
Replies: 10
Views: 6900

Re: TRX1 PA Board Bias adjustment

Marc, There must be some very simple silly mistake in your measurement because this should be very easy to measure. The bias trimmer pots are 10 kohm trimmers and typically they will go clearly below 100 ohms at both end when turning fully to corresponding direction. Let's start from the beginning a...
by OH7SV
22 Nov 2012 18:51
 
Forum: Juma Discussion
Topic: TRX1 PA Board
Replies: 10
Views: 6900

Re: TRX1 PA Board

Marc,

They should go lower. Are you sure that you are measuring from gates?
Maybe it is easier to locate the trimmers center leg. Pse measure resistance directly from trimmers center leg to GND and turn the trimmers to minimum ohms reading.

73 Matti OH7SV
by OH7SV
22 Nov 2012 16:26
 
Forum: Juma Discussion
Topic: TRX1 PA Board
Replies: 10
Views: 6900

Re: TRX1 PA Board

Marc, The point is that you should turn the bias trimmers to minimum voltage before powering the PA. Pse measure the resistance from gates (TR1, TR2, TR3) to GND and adjust the corresponding bias trimmers until ohm meter reading is indicating lower than few hundred ohms. You can use any GND joint fo...
by OH7SV
21 Nov 2012 18:15
 
Forum: Juma Discussion
Topic: TRX1 PA Board
Replies: 10
Views: 6900

Re: TRX2 general TX coverage

Edgar, JUMA TRX2 and TRX2A standard firmware in is not limiting TX frequency coverage. You can transmit on any frequency from 1.5MHz to 30MHz. Note that the PA low-pass filters are optimized for ham bands 1.8MHz - 28MHz. This may mean more harmonics on non ham frequencies especially in low edge of t...
by OH7SV
19 Nov 2012 20:52
 
Forum: Juma Discussion
Topic: TRX2 general TX coverage
Replies: 2
Views: 2492

Re: PA100-D with an Elecraft KX3

David,

You may try different drive levels (2.5W-10W) from KX3 and adjust JUMA PA100 gain accordingly to get desired power ouput.
I think this way you will get proper operation of the frequency detection also on 15m and 17m.

When you have tested, pse let me know your findings.

73 Matti OH7SV
by OH7SV
22 Aug 2012 02:37
 
Forum: Juma Discussion
Topic: PA100-D with an Elecraft KX3
Replies: 6
Views: 7580

Re: TRX2 1st filter and sidetone level

Hello Laurent, You are right that the 1st filter is a "roofing" filter which is in the AGC loop. We know the properties of the 1st filter. It is compromize of selectivity and noise. Noise is the reason for its response because sharp active filters are easily bad noise generators. I have be...
by OH7SV
19 Aug 2012 05:53
 
Forum: Juma Discussion
Topic: TRX2 More narrow filter
Replies: 5
Views: 6770

Re: PA100 PA Current Resistor

Dave,

The R7 resistor is single 0.005 ohm current sense resistor. The two 0.010 ohm resitors are remains when 0.005 ohm was not available. You can keep the two 0.010 ohms in parallel.

73 Matti OH7SV
by OH7SV
19 Aug 2012 05:39
 
Forum: Juma Discussion
Topic: PA100 PA Current Resistor
Replies: 1
Views: 3067
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