Hi All:
 
Steve Ratzlaff and I have been testing a homebrew NDB receiver
designed by my brother Russell Robins N8HOQ. This receiver takes a
somewhat different approach than the one Mitch Lee used with his
portable receiver several years ago. Steve has been an active and
invaluable co-developer on this project.
 
Since Russ lives about 400 miles away from me, I only got my hands on
my brother's prototype version of the rig over the weekend and am
having a lot of fun putting it through its paces. A full technical
write-up and schematic will be available shortly for those who may
want to try "rolling their own" receiver. A PCB board is also being
developed but has yet to be tested.
 
The basic features of the receiver are:
 
1. 150 Hz IF filtering enabling full use of Spectran,or similar programs.
2. Built-in 6-10 Hz Ratzlaff active audio filter with in/out
selectable from panel switch.
3. 1 Hz tuning with precision and stable DDS VFO with digital
frequency read-out.
4. Built-in nine-pole low-pass filter with 6db roll-off at 510 kHz.
5. More than adequate MDS at -140dbm.
6. Ultra-quiet audio section.
7. Sufficient audio to drive either headphones or speaker.
8. Provision for RF gain if used with "monster" longwire antennas.
9. VFO A/B.
10. Multiple memories.
12. Readily calibrated to within 1Hz via WWVB from front panel.
 
My initial impressions of the rig are overwhelmingly favorable. It is
extremely portable and very nearly the equal in performance to my R-75
- including all of its cumbersome external paraphernalia (Timewave
DSP-599zx and Ratzlaff 8 Hz audio filter). This rig will totally blow
away any commercially-made portable receiver, including the legendary
Sony 2010/2001-D, for NDB DXing on the go.
 
In addition to the receiver, Russ also built a version of Roelof
Bakker's active whip system in a matching Hammond mini-chassie that
matches the rig. While Russ was visiting here over the weekend, we
hauled this whip up into a convenient tree and connected it to the
homebrew receiver (unofficially dubbed the PLFR – "Portable LF
Receiver"). This was to be the acid test since there is a 10 kW
"X-Band" BCB station less than half-a-mile from the test location. The
built-in LPF kept BCB breakthrough to a minimum and allowed reception
of DX targets like PIE-400 in Colombia and RB-350 in the far north of
Canada. It was especially nice to use the rig in conjunction with
Spectran. This allowed us to see interesting signals and then center
them squarely in the bandpass of the receiver's audio filter.
 
I have attached a photo of the receiver as built by my brother. It
shows the receiver and active whip housing next to Russ' laptop
running Spectran.
 
I will forward the technical details as soon as possible. You can also
contact Russ directly at pnpjunction(at)aol.com for more information.
 
73,
 
Andy Robins KB8QGF
Kalamazoo, Michigan USA
 

Kyllä nuo vanhatkin radiot on suhteellisen helppo korjata. Kaikille komponenteille löytyy vastineita tänä päivänä. Ainoan isomman ongelman tekee sen aikaiset prosut, niitä kun ei tunnu saavan mistään. On tuohonkin muutakiin rigeihin keksitty apu, tehdään uudemmasta, esim. PIC-prosessorista tilalle uusi, näitä on nähty esim. Yaesu FT757 rintamalla.
 
 Itsekin ostin muutama vuosi sitten hyvin rikkiäisen FT-757GX:n joka jo reilusti yli 20 (taitaa olla 25) vuotta vanha mutta kyllä siihen vain osat löytyi. Töitä oli kyllä tehtävä vastaavien löytämiseksi.
 
 Mutta homebrew radionsa kyllä pystyy korjaamaan, ellei ole unohtanut tehdä dokumentaatiota ja sitten 10 vuoden päästä kun sitä pitäisi korjata niin ihmetellään mitä siellä sisällä on  
 
t: Janne

Russ on luvannut ensi viikolla kytkennät ja muut lisäkuvat näytille.
 
Odotamme jännityksellä
 
kari

Onko kenelläkään tietoa, mihin tämä projekti kuoli?
 
 
 
Teijo