Performance test QRP+

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From: RICHARD HIEBER (SZ0026@daphne.rrze.uni-erlangen.de)
Date: Tue Mar 14 1995 - 10:13:59 EST


Hi gang,

Roeland, PA0RBC, sent me some measurement results on the QRP Plus
transceiver from Index Labs via PR and explicitly permitted its
distribution to QRP-L. I don't own this type of rig yet, but I am very
interested, and so is probably half of the list, considering the recent
group purchase.

Please take the info as it is. I am not the one who did the measurements
and I am not in a position to check them.

Vy 72 de Richard Hieber, DL8MFQ/AA8CP
sz0026@daphne.rrze.uni-erlangen.de

-----------------------------------------------------------------------------
PA0RBC > DL8MFQ 09.03.95 23:38 227 Lines 9911 Bytes #180 @DB0SIF.#HES.DEU.EU
Subj: PERFORMANCE TEST QRP+
Path: !DB0SIF!DB0GV!DB0LJ!DB0SGL!DB0END!DB0ACC!PI8DAZ!PI8MBQ!PI8DHR!
Sent: 950309/2138Z @:PI8DHR.#NH1.NLD.EU #:34703 [DEN HELDER] $:34703_PI8DHR

>From: PA0RBC@PI8DHR.#NH1.NLD.EU
To : DL8MFQ@DB0SIF.#HES.DEU.EU

Hello Richard, last Monthday I did some measurements on the plus.
The day after, Robert, PA3BHK did send me a suggested modification
he have got via Bruce fm Index to suppres the harmonics above transmitting
then 30m band, but the spurious is strange enough several MHz below the
transmitting freq. Possible coming fm downmixing?
Okay, it stay a nice trcvr and the solutions will come from the hams also
to Bruce.
Read!:

    Performance Test Index Laboratories QRP + trcvr, serialno. 432
    --------------------------------------------------------------

Freq. ! 12Vbattery ! 13.5 Vbattery ! SINAD ! Freq. dev. ! Harmonics
KHz ! Pcw Ib ! Pcw Ib ! 10dB(uV) ! display freq.! & Spurious
----------------------------------------------------------------------------
 1950 5.65 1.2 ! 7.83 1.4 ! 0.567 ! 44 ! -48 dB
 3560 5.96 1.2 ! 7.52 1.4 ! 0.521 ! 18 ! -57 dB
 7030 6.18 1.32 ! 8.95 1.68 ! 0.443 ! 40 ! -42 dB
10130 7.93 1.32 ! 10.00 1.5 ! 0.475 ! -40 ! -22 dB
14060 6.00 1.32 ! 10.00 1.75 ! 0.484 ! 40 ! -32 dB *
18130 4.63 1.32 ! 8.02 1.75 ! 0.494 ! - 5 ! -28 dB *
21060 3.64 1.32 ! 4.88 1.55 ! 0.494 ! 106 ! -30 dB *
24920 4.74 1.32 ! 7.4 1.62 ! 0.500 ! -30 !
28060 3.6 1.32 ! 6.21 1.60 ! 0.535 ! 28 ! -25 dB *
28900 3.39 1.32 ! 5.89 1.58 ! 0.529 ! 28 ! -25 dB *

- Frequency accuracy measured direct after switching
  from memory to memory without finetuning with the big knob.
  The receiver comes always on the same freq. if you do that, nice to
  find fixed freq. channels as beacon freqs.
- Phasenoise let the synthesizer go about 2 Hz up and down during short times.
- The given harmonics and spurious in the table are the most
  bad level measured.
- (*) Spurious below Transmitting frequency.

Nearby SSB (A3J) measurements in a 10 KHz Span, BW 100 Hz, VBW 10 Hz.
---------------------------------------------------------------------
  Reference: single tone 800 Hz power max. 34 dBm (2.5 W)/80 meter band.
  ----------------------------------------------------------------------
- Microphone input impedance measured for 1000 Hz is 600 ohm.
- Minimum inputpower for maximum RF power: -53 dBm (10 mVtt/1 KHz).
- Carriersuppression -28 dB below single tone.
- Created 3th order products -48 dB below single tone.
- Created 5th order products -68 dB below single tone.

  Reference: double tone 800/2200 Hz, each tone +30 dBm (1W).
  -----------------------------------------------------------
- Carriersuppression -23 dB below the 2-tones.
- Between the 2 tones an unknown signal -18 dB below the 2 tones.
- Created 3th order products -32 dB below 2 tones.
- Created 5th order products -48 dB below 2 tones.

The ALC keeps the outputpower and products around the same level
if you try to overdrive the microphone level.

Automatic Gain Control.
-----------------------
Measured on 14100 KHz increasing the R.F. signal from
1uV (-107dBm) to 10mV (-27dBm) gives an increase of 4 dB.
Also a signal of 1.26V (+15dBm) don't give audio distorsion.
AGC works very good with a slow decay of about 1 second.

Maximum audio output 1000 Hz.
-----------------------------
The maximum audio measured over the 8 ohm speaker is 1.65 V (340mW).
Maximum audio over the external phone jacket 3.2 mm is 10 mW//3 ohm.

SCAF-filter.
------------
Measuring the maximum audio obtained during the settings below:
Bandwith Peaking on
-------- ----------
100 Hz 600 Hz Don't select a bandwith smaller then 300 Hz if
200 Hz 650 Hz like to hear a beatnote of 800 Hz or higher.
300 Hz 700 Hz Bandwiths > 300 Hz are okay for 800 Hz tone.
500 Hz 680 Hz
For example in my case: If you like to hear the 14.100 MHz beacon-chain
you read in the freq. display 14099.4, then you can hear on all
bandwiths the 600 Hz beatnote well.

S-meter accuracy: Measured on 14100 Khz nearly same results on 3560 KHz.
----------------
S1 S4 10 dBuV S7 23.1 dBuV The figures are in dB over
S2 3.4 dBuV S5 14.5 dBuV S8 26.8 dBuV 1 uV signal.
S3 6.3 dBuV S6 19.1 dBuV S9 31.9 dBuV

Strongsignal mixing products Fant 14.1 MHz 10mV (-27dBm).
---------------------------------------------------------
Under and below the receiving freq. you hear birdies on 14.102, 14.109
14.114, 14.121 also in the same ratio below 14.1 MHz.

Unwanted radiation on the Antenna SO239 connector during receive.
-----------------------------------------------------------------
Signals of -52 dBm and lower are detectable in the range from 1-500 MHz.

Break-in (QSK) during CW.
-------------------------
You can good hear 'dit and dah' between your own CW-transmissions.

Remarks:
--------
It is advisable to use specially for frequencies 10 MHz up a high-Q
bandpassfilter to suppress unwanted radiations.
Also Magnetic loop or Toroidal antennas (see Radio Communications
April 1994, page 13 etc.) are preferred.
                          
Used Measuring equipment:
-------------------------
- Rohde&Schwarz Radiocommunication analyzer 0.1...1000MHz, CMTA54.
- Racal-Dana 9083, 2-tone signal source.
- Hewlett Packard HP8568B Spectrum Analyzer.
- Two coaxial power-attenuators 20 dB.
  
'73 es '72 fm PA0RBC@PI8DHR.NLD, Roeland, Den Helder, March 1995.

Hello Peter, I've got these article via Robert, PA3BHK who did
write letter to Bruce.

>From Index, KG7CR to PA3BHK to PA0RBC near an idee of N6CM.
Dear Mr. Van der Zaal (PA3BHK):
Thank you for your letter regarding the QRP Plus transceiver.
We are working to improve the second harmonic rejection on the
three upper bands. I enclose schematics of filters which we plan
to use in future production. They meause at least -48dbc for
second harmonic.
I am not sure about the non-harmonic spurs. We have seen some if
the CW power is turned up high (7 or 8 Watts) causing the final
to be overdriven.
We are working on a new prom which will include smaller keyer
speed steps. I will write when it is ready.
The signal on the top PCB is about 40mW. It should be a good
place to connect a transverter.
Sincerly, Bruce Franklin.

The change is not too difficult to implement on the existing PCB.
The steps are as follows.
- Replace L11 with 2 100nh chokes in parallel.
- Lift C41 and C42 leads from the pads where they join and insert
  330 pf between the two caps and the PCB.
- Install a 470 pf NPO with very short leads (I used a chip) from
  the IF terminals of U3 and GND.

>From N6CM, Robert E. Friess to Bruce Franklin fm Index.
More Harmonics.
As supplied the harmonic performance of the radio is pretty marginal
as shown in the preceding tables. In analysing the 3 highest frequency
lowpass filters. I found that hte attenuation at the 2nd harmonic was
not as high as it could be and that the cutoff was very close to the
desired output frequency increasing loss and probably, with component
tolerance variation, a production problem with some radios.
I redesigned each of the filters as Cauer filters which provide zeros
of transmission. With the resultant steeper attenuation slope.
I was able to move the cutoff out a little which reduced insertion loss
and in production would be an easier design to reproduce. The before
and after performance is given in the table below.

Band (MHz) Pwr Out (Wtts) PwrOut (Wtts) 2nd Har(dBc) 2nd Har(dBc).
              Before After Before After
 10.1 9 13 -30 -55
 14 7 8 -48 -48
 18 9 10 -30 -42
 21 7 8 -40 -40
 24 7.5 7 -35 -50
 28 5 5 -45 -55

All measurements were made with CW pwr turned all the way up and if
the power were readjusted the same as before the improvement would
be even greater because of less distorsion in the amplifier.
The changes are simple, I would be glad to provide you with
documentation if you are interested.
That still leaves the problem with the tone in the audio. I haven't
figured that one out yet. Also, I believe that it would be pretty
easy to activate the ALC for CW. I'll let you know if it works.

         0--!------18pf----!----- 47pf----!----0
            !-----300nh----!---- 210nh----!
10/12 M 68pf 7T 140pf 6T 47pf LPF1B
            ! ! !
         0-------------------------------------0

         0--!------22pf----!------68pf----!----0
            !-----390nh----!---- 270nh----!
15/17 M 100pf 8T 180pf 6.5T 56pf LPF2B
            ! ! !
         0-------------------------------------0

         0--!------68pf----!-----220pf----!----0
            !-----520nh----!---- 300nh----!
20/30 M 100pf 10T 180pf 7T 56pf LPF3B
            ! ! !
         0-------------------------------------0

         0--!------22pf----!------68pf----!----0
            !-----420nh----!---- 330nh----!
15/17 M 120pf 220pf 100pf LPF2C
            ! ! !
         0-------------------------------------0

'73 fm Roeland PA0RBC @ PI8DHR, March 7, 1995, Den Helder.

P.S.:
No problems with audio pop of the agc, works well.
Birdies are detectable on dummyload but weak and acceptable, must still check
all bands Richard.
I did not yet try out the Iambic keyer.
TX outband transmissions are not possible.
Waiting with mods (1 year guarantee)
Till so far, shall check your questions again but do read it now to adres
this message to you.
Bye Richard '73 fm Roeland.


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