I've done dozens of Cobra 29's over the years, and was always partial to 2SC1969 finals. However, I recently got the opportunity to work on the following FACTORY MOSFET'ed Galaxy transceivers:
- Galaxy DX-98VHP which has three (3) IRF-520's (1 as a driver and twin finals) driving an amplifier section consisting of eight (8) IRF-520's for a total of 11 of these amazing lil puppies.... and a
- Galaxy DX-2547 CB Radio AM/SSB Base Station with a single IRF-520 final transistor (I think the driver may have been a MOSFET as well, but I can't recall)
Anyway... the DX-98VHP exhibited super performance on both AM and SSB. It also incorporated an internal cooling fan in the amplifier section which will no doubt help keep the 8X520's cool under load. If I had my 'druthers', I'd snag up one of these in a heartbeat. What's not to love?
The DX-2547 was also impressive. The factory .15 uV SSB receive sensitivity gives this thing some EARS! Can't remember the RX transistor number but it was NOT the typical 2SC1674.... it was quieter... was NOT a 2SC2999, but was an equivalent with even better gain. Also, and here's what impressed me about the MOSFET final, when I adjusted the ALC for SSB output power, the radio would do over 30 watts SSB (factory Galaxy stock mic) on the internal AC power supply off of a single IRF-520. Not knowing the current output rating of the AC supply, I turned the rig down to 22W SSB PEP.
30W SSB with the turn of a VR POT off of a single IRF520 seemed pretty impressive to me; and from what I've read about the IRF520, it looks like it can handle every bit of it. (Again, my only fear was the factory power supply. Anybody know the current handling capacity of the internal AC to DC pwr supply in the DX-2547?)
So, WHY am I starting to like MOSFETS? Well, over the years I've either repaired, modified, converted or enhanced dozens & dozens (perhaps hundreds) of radios, mostly Cobra 29's. I've always been partial to the 2SC1969 final, but in the past few 10-12 radios I've done, I've begun to incorporate the IRF-520's in an increasing number of Cobra 29's. Here's what I've found:
- Older Cobra 29 LTD's (especially Philippines), GTL's and XLR's: seem to prefer the 2SC1969 for higher output power. I've gotten over 45 watts out of these radios.
- Newer 29 LTD's (and all SoundTrackers, Nightwatches, WX band radios): seem to respond BEST to the IRF520 mod (with the companion part designed for the ERF-2030). With these (especially SoundTrackers) it seems they respond best to maintaining a deadkey in the range of 2-4 watts and allowing 'some' swing into the 8-12 RMS range. Typical yield is about 25-35 watts PEP on modulation.
- 1990's and new Made in CHINA Versions: these are truly the WILDCARDS. Some like the 2SC1969 mod, some seem to like the IRF520. Since the 520's are plentiful, less expensive, and easier to install, I think I'm gonna stick to this arrangement unless any of you can provide reasons for sticking with an NPN bipoloar final.
So, I guess I'm really starting to like the MOSFETs especially for the following reasons:
1. They are becoming more and more prevalent from the FACTORY (especially in the Galaxy chassis rigs, and in the Export radios)
2. Many radios respond well to them (even the Cybernet chassis as seen on YouTube)
3. They are (certainly) less expensive then 2SC1969 or equivalents
4. They are 'easier' to install (relative) in a Cobra 29 chassis
5. They have a higher power dissipation rating than a 1969
6. A single finaled MOSFET can develop higher output power than a single finaled 2SC1969 in the Galaxy chassis with just the turn of a pot(s), whereas you'd have to make some circuit modifications to get the 2SC1969's to 'come-to-life' in an older radio
7. 2SC1969's are no longer being manufactured. The closest we can get from the 'factory' is the 20W Eleflow version.
8. In a pinch, the IRF510 (15W version) is readily available from our local Radio Shack. (Try finding a genuine Mitsubishi 2SC1969 from Radio Shack!, lol
9. I've gotten "burned" in the past with counterfeit 2SC2166 and 2SC1969's either NOT working at all, or failing to provided desired gain or power dissipation requirements. So far, (knock wood) all the 510's and 520's I've tried have worked flawlessly.
10. MOSFETs are the 'future'... even though I constantly refer to myself as an "analog guy in a digital world", I either need to get with the program or be left behind.
11. Just about every late-model Ham transceiver coming out of Japan have been using MOSFETs for quite some time. They develop good power: CHEAPLY (I suppose.) I remember the "old days" when blowing the finals in a ham transceiver could cost "big bucks" for the transistors. Recently, I needed to change the HF finals only in my Icom 706MKIIG (MOSFETS) and I think the pair cost me less than $60 from RF Parts. (I probably could've done better price-wise if I had shopped around, or sourced them from overseas).
Seems to me like Galaxy, RCI - Ranger, RF Limited, and the 'Exports' have all already jumped on the MOSFET bandwagon. In fact, the ONLY NEW radios I'm seeing still coming from the factory with NPN 2SC2078 final transistors are Cobra, Midland, and Uniden. And, IF you want to significantly increase the output power of the 2078 equipped transceivers, the choice is clear: MOSFET POWER.
What's NOT to love? What do you guys think???
- Galaxy DX-98VHP which has three (3) IRF-520's (1 as a driver and twin finals) driving an amplifier section consisting of eight (8) IRF-520's for a total of 11 of these amazing lil puppies.... and a
- Galaxy DX-2547 CB Radio AM/SSB Base Station with a single IRF-520 final transistor (I think the driver may have been a MOSFET as well, but I can't recall)
Anyway... the DX-98VHP exhibited super performance on both AM and SSB. It also incorporated an internal cooling fan in the amplifier section which will no doubt help keep the 8X520's cool under load. If I had my 'druthers', I'd snag up one of these in a heartbeat. What's not to love?
The DX-2547 was also impressive. The factory .15 uV SSB receive sensitivity gives this thing some EARS! Can't remember the RX transistor number but it was NOT the typical 2SC1674.... it was quieter... was NOT a 2SC2999, but was an equivalent with even better gain. Also, and here's what impressed me about the MOSFET final, when I adjusted the ALC for SSB output power, the radio would do over 30 watts SSB (factory Galaxy stock mic) on the internal AC power supply off of a single IRF-520. Not knowing the current output rating of the AC supply, I turned the rig down to 22W SSB PEP.
30W SSB with the turn of a VR POT off of a single IRF520 seemed pretty impressive to me; and from what I've read about the IRF520, it looks like it can handle every bit of it. (Again, my only fear was the factory power supply. Anybody know the current handling capacity of the internal AC to DC pwr supply in the DX-2547?)
So, WHY am I starting to like MOSFETS? Well, over the years I've either repaired, modified, converted or enhanced dozens & dozens (perhaps hundreds) of radios, mostly Cobra 29's. I've always been partial to the 2SC1969 final, but in the past few 10-12 radios I've done, I've begun to incorporate the IRF-520's in an increasing number of Cobra 29's. Here's what I've found:
- Older Cobra 29 LTD's (especially Philippines), GTL's and XLR's: seem to prefer the 2SC1969 for higher output power. I've gotten over 45 watts out of these radios.
- Newer 29 LTD's (and all SoundTrackers, Nightwatches, WX band radios): seem to respond BEST to the IRF520 mod (with the companion part designed for the ERF-2030). With these (especially SoundTrackers) it seems they respond best to maintaining a deadkey in the range of 2-4 watts and allowing 'some' swing into the 8-12 RMS range. Typical yield is about 25-35 watts PEP on modulation.
- 1990's and new Made in CHINA Versions: these are truly the WILDCARDS. Some like the 2SC1969 mod, some seem to like the IRF520. Since the 520's are plentiful, less expensive, and easier to install, I think I'm gonna stick to this arrangement unless any of you can provide reasons for sticking with an NPN bipoloar final.
So, I guess I'm really starting to like the MOSFETs especially for the following reasons:
1. They are becoming more and more prevalent from the FACTORY (especially in the Galaxy chassis rigs, and in the Export radios)
2. Many radios respond well to them (even the Cybernet chassis as seen on YouTube)
3. They are (certainly) less expensive then 2SC1969 or equivalents
4. They are 'easier' to install (relative) in a Cobra 29 chassis
5. They have a higher power dissipation rating than a 1969
6. A single finaled MOSFET can develop higher output power than a single finaled 2SC1969 in the Galaxy chassis with just the turn of a pot(s), whereas you'd have to make some circuit modifications to get the 2SC1969's to 'come-to-life' in an older radio
7. 2SC1969's are no longer being manufactured. The closest we can get from the 'factory' is the 20W Eleflow version.
8. In a pinch, the IRF510 (15W version) is readily available from our local Radio Shack. (Try finding a genuine Mitsubishi 2SC1969 from Radio Shack!, lol
9. I've gotten "burned" in the past with counterfeit 2SC2166 and 2SC1969's either NOT working at all, or failing to provided desired gain or power dissipation requirements. So far, (knock wood) all the 510's and 520's I've tried have worked flawlessly.
10. MOSFETs are the 'future'... even though I constantly refer to myself as an "analog guy in a digital world", I either need to get with the program or be left behind.
11. Just about every late-model Ham transceiver coming out of Japan have been using MOSFETs for quite some time. They develop good power: CHEAPLY (I suppose.) I remember the "old days" when blowing the finals in a ham transceiver could cost "big bucks" for the transistors. Recently, I needed to change the HF finals only in my Icom 706MKIIG (MOSFETS) and I think the pair cost me less than $60 from RF Parts. (I probably could've done better price-wise if I had shopped around, or sourced them from overseas).
Seems to me like Galaxy, RCI - Ranger, RF Limited, and the 'Exports' have all already jumped on the MOSFET bandwagon. In fact, the ONLY NEW radios I'm seeing still coming from the factory with NPN 2SC2078 final transistors are Cobra, Midland, and Uniden. And, IF you want to significantly increase the output power of the 2078 equipped transceivers, the choice is clear: MOSFET POWER.
What's NOT to love? What do you guys think???
