Repairing the Perseus' Power Supply

 After more than a decade of service, the switching power supply of my Perseus SDR failed. Symptoms included receiver freezing frequently, with the host PC showing error messages such as "Device not recognized". Apparently, this is a frequent fault.

So, I decided to open the power supply and fix it. With this document I want to share my experience, but first let me state it very clearly: do it at your own risk. I will accept no liability for any damage you will do to your radio, to yourself or to this sector of the Universe by following the procedure outlined in this document.

The problem

The culprits are two low-voltage electrolytic capacitors (330uF, 25V) of an unknown (to me) brand (Luxon); with time they age and the ESR reaches stellar values (up to 300W have been measured). The output voltage becomes unstable or too low to properly power the Perseus.

The cure

The power supply must be opened carefully to minimize damage. The two shells are not glued, but there are plastic snap fasteners that hold them together. I used a large, flat screwdriver to force them open (with minimal damage) from the back (where the cable exits) – see Figure 1. 

Figure 1: I opened the case from the back with minimal body damage.

Once opened, the two capacitors circled in red in Figure 2 must be replaced with good-quality new ones (330uF – 25V). Mind their size since space is at premium. Close the power supply, check the output voltage (5.2 V) and you’re back in business.

Figure 2: the offending capacitors, circled in red.

Inseguendo la propagazione – negli ultimi mesi sempre più elusiva – ho “riscoperto” una vecchia conoscenza, la rete di beacon sincronizzati (IBP - International Beacon Project) gestita dalla Northern California DX Foundation (NCDXF).

Si tratta di una rete nata nel 1979 e recentemente ristrutturata con nuovi controller (basati su Arduino) e nuove radio (IC7200); oggi è costituita da 18 beacon distribuiti su tutto il pianeta ed operanti sulle frequenze di 14.100, 18.110, 21.150, 24.930 e 28.200 MHz.

Ogni beacon trasmette per 10 secondi, poi subentra il beacon successivo; l'intero ciclo si ripete quindi ogni 3 minuti, 24 ore al giorno, 7 giorni su 7. Ogni beacon si identifica in CW, utilizzando la massima potenza (100 W), poi invia delle “linee” a potenza decrescente di 10, 1 e 0.1 W.

Chi fosse interessato troverà maggiori informazioni su https://www.ncdxf.org/pages/beacons.html

Io utilizzo una pratica applicazione Android (ma ce ne sono anche per Apple, Windows e Mac) che mi dice in tempo reale quale beacon sta trasmettendo sulla frequenza da me selezionata.

C’è da dire che oggi esistono parecchi sistemi per il monitoraggio in tempo reale dello stato della propagazione, cito ad esempio WSPR ed il Reverse Beacon Network. Rispetto a questi sistemi – peraltro potentissimi – la rete IBP presenta diversi vantaggi: è attiva 24/7; utilizza trasmettitori ed antenne con caratteristiche tutte uguali e tipiche della stazione HAM “entry level” (100 W e verticale); può essere utilizzata in sola ricezione (a differenza del Reverse Beacon); non necessita di PC (a differenza del WSPR).

Modifying the FRG-7000

Introduction

The Yaesu FRG 7000 is a colorful, vintage receiver that is still fun to use. The main drawback when used in AM mode is the availability of only one IF bandwidth, that is way too wide (9kHz at –6dB, measured) in crowded band conditions (What ? “Crowded bands” in 2017 ?). The narrow filter (2.8 kHz at – 6dB) is accessible only in USB/LSB modes.

However, this limitation can be overcome with a very simple modification, that is absolutely not-invasive and completely reversible. With this modification when you select the AM mode the receiver uses the Wide Filter, while when you select the AM-ANL mode the receiver uses the Narrow Filter.

But first let me state it very clearly: do it at your own risk. I will accept no liability for any damage you will do to your radio, to yourself or to this sector of the Universe by following the procedure outlined in this document.

The mod

Since the filters are selected electronically by activating a diode, the modification is very simple: just “cut” a connection on the “mode” switch and rewire it. This will allow you to select the Narrow Filter in AM-ANL mode, while the standard AM mode uses the Wide Filter.

The mode switch is easily accessible from underneath the radio, there is no need to dismount anything apart removing the receiver’s cover; the photo below shows the position of the mode switch (circled in red).

In the schematic below the modification is shown: just “cut” a connection (red cross) on S2(e) switch and rewire it with the blue wire. The section (e) of switch S2 select the desired IF filter (CF01 –wide-  or CF02 –narrow-) by grounding a diode (and hence activating it).

As standard, CF01 is selected for AM and AM-ANL modes, and CF02 for USB and LSB modes. By rewiring section (e), we activate CF01 only for AM, and CF02 for USB/LSB/AM-ANL; as simple as that !

Please note that I kept the ANL circuit operative, since I could hardly notice its effect; if you want, you can disable it but then the modification will be more invasive and you will need to rewire also section (a) of S2.

On the left the band switch before the mod. The connection that need to be interrupted is the one circled in blue, easily accessible, where the white-and-blue wire is connected.

There is no need to dismount the switch.

The two pins of the switch are soldered together; I cut the wire and then used a de-soldering pump to remove the solder and separate them.

On the right the band switch after the mod. Note the added green wire that jumpers the fourth (and last) pin of the switch (AM-ANL position) to the first and second pins (USB/LSB position), i.e. to the white-and-brown wire.

The white-and-blue wire is now connected only to the third pin (AM position).

Ascolti milanesi

Ascolti milanesi senza pretese. I canali eritrei "intrusi" nella banda radioamatoriale dei 40 metri sono spesso oggetto di pesante noise-jamming (dall'Etiopia, forse ?), il che rende inutilizzabile una banda larga dai 10 ai 20 kHz attorno alla frequenza centrale dell'emittente... se ne sentiva davvero il bisogno !

 5915 20:16 21/10 Zambia NBC, Lusaka, talk, VV. Fair.  (SIO 344).
 5950 19:53 11/10 Voice of Tugray Revolution, Ethiopia, local music, VV. At 19:58 whiped out by KBS (via France) signing in. Good. SIO (444).
 5995 20:20 21/10 RTV du Mali, Bamako, talk, local music, VV. Fair signal, low modulation. (SIO 343).
 6090 20:17 11/10 Amhara State Radio, Ethiopia, local music, talk, VV. Fair. (SIO 343)
 6110 20:02 11/10 R. Fana, Ethiopia, local music, talk, VV. Good. (SIO 444).
 7145 16:40 21/10 Heavy jamming (against Voice of the Broad Masses, I suppose), spanning almost 20 kHz, extremely strong, messing up the 40 metres ham band.
 7185 16:40 21/10 Heavy jamming, spanning almost 10 kHz, strong, messing up the 40 metres ham band.
11975 16:20 21/10 A.W.R. via Sri Lanka, sermon, EE. Fair. (SIO 343).
12065 20:04 21/10 R.Australia, Shepparton, ABC news, EE. Good. (SIO 444).
15124 16:10 21/10 C.R.I. via Mali, TK, AA. Exactly 1 kHz below nominal frequency. Good. (SIO 354).
15235 16:07 21/10 Channel Africa, South Africa, news, FF. Very good. (SIO 455).
15345 16:12 21/10 R. Cairo (I suppose), just buzzing noise, no modulation, as usual... do they have engineers there ?


73,

Michele IZ2EAS - Milano

RXs (modern) : Perseus, Drake R8E, Icom R72
RXs (vintage): Collins 51S1, Drake R4C, BC348R, Russian R-326
Antenna:    Cushcraft R8 vertical (ham bands, 9 metres high)
More infos: https://www.qrz.com/db/iz2eas
Facebook:   https://www.facebook.com/michele.iz2eas

Qualche ascolto autunnale

Ciao,
un piccolo log con gli ascolti della settimana appena passata. Condizioni così così a Milano, con il solito rumore elettrico sempre presente.

 4765 04/10 19:33 R.Tajikistan, talk, VV. Poor. (SIO 232)
 4835 04/10 19:24 A.B.C. Alice Springs, Australia, talk, EE. Fair-to-poor. (SIO 243)
 6005 07/10 19:28 Radio 700, Germany, pop mx. Fair. (SIO 433)
 6070 05/10 18:20 I.B.C. via Channel 292, posta degli ascoltatori, II. Good. (SIO 454)
 6130 06/10 19:08 Trans World Radio, Swaziland, religious songs, TK, VV. Fair (SIO 343)
 6150 09/10 06:59 Europa 24, Germany, music, ID in German at 07:00, news in German. Good. (SIO 444)
 6180 09/10 06:50 R.Nacional Brasilia, soft songs (lulling listeners to sleep?) ID, PP. Fair. (SIO 344)
 6195 04/10 20:02 V.O.A. via Botswana, African Beat, beautiful African music, EE. Good.(SIO 444)
 6267 07/10 19:48 Mustang Radio, pop mx, ID in EE, e-mail address. Very good. (SIO 544)
 6285 08/10 20:25 Radio Focus International, mx, ID and jingle in EE. Good. (SIO 444)
 6300 09/10 08:02 Radio Quintus, Arnhem, Netherland, music, frequent IDs in EE. Fair. (SIO 343)
 6305 09/10 20:33 TRX Radio, music, multiple ID in English "TRX radio on shortwave". Fair. (SIO 333)
 6320 06/10 18:28 Radio Oleg, two men talking, commenting on what a stupid hobby radio listening is (!), ID, mx, EE. Good. (SIO 444)
11735 04/10 10:46 Zanzibar B.C., Tanzania, African mx, VV. Good. (SIO 454).
15345 06/10 19:40 R.A.E., Argentina, historical news, II. Fair. SIO (353).

73,

Michele IZ2EAS - Milano

RXs (modern) : Perseus, Drake R8E, Icom R72
RXs (vintage): Collins 51S1, Drake R4C, BC348R, Russian R-326
Antenna:    Cushcraft R8 vertical (ham bands, 9 metres high)

Ascolti metropolitani

Ascolti fatti in relax, da Milano, in mezzo al rumore cittadino, principalmente con il Drake R8E. Molto attivi i 49 metri al mattino; Radio Habana Cuba ha attive 4 (!) frequenze in parallelo, con il programma in inglese. R. Nacional dal Brasile a bomba.


 6000 08/09 05:16 R. Habana Cuba, talk // 6165, 6100, 6060, EE. Fair (SIO 433).
 6060 08/09 05:11 R. Habana Cuba, talk // 6165, 6100, 6000, EE. Good (SIO 454).
 6100 08/09 05:06 R. Habana Cuba, talk // 6165, 6060, 6000, EE. Very good (SIO 555).
 6135 08/09 05:07 R. Aparecida, talk and music, PP. Fair (SIO 354).
 6165 08/09 05:02 R. Habana Cuba, ID, talk // 6100, 6060, 6000, EE. Good (SIO 454).
 6180 07/09 05:20 R. Nacional Brasil, music program "Madrugada Nacional", PP. Very good (SIO 454) 
15344 07/09 19.05 R. Argentina al Exterior, TK, II. Poor (SIO 242).

Michele IZ2EAS - Milano

RXs (modern) : Perseus, Drake R8E, Icom R72
RXs (vintage): Collins 51S1, Drake R4C, BC348R, Russian R-326
Antenna:    Cushcraft R8 vertical (ham bands, 9 metres high)
More infos: https://www.qrz.com/db/iz2eas
Facebook:   https://www.facebook.com/michele.iz2eas

Per gli amanti della radio digitale...

I vigili del fuoco olandesi (e non solo) "scaricano" la radio digitale e tornano alla FM analogica.
La ragione? E' talmente inaffidabile da mettere in pericolo la sicurezza di pompieri e civili.
Meditate, talebani del D-Star, meditate !

http://hamgear.wordpress.com/2013/11/09/dutch-fire-department-ditches-c2000/