HBR-influenced receiver

[w3jn]

There are others...  the 6JH8 and 6ME8 for starters.  The 6ME8 apparently wants a relatively high screen voltage though - 300V.

Swan subbed the 7360s in their HF rigs for 6JH8s in later production runs.

[KI4YAN]

It is not that I am against the pullen mixer, it is simply that I am looking at all options. I have used this cascode mixer before, and it is often used today in solid state equipment is all.

[KM1H]

How do you propose to neutralize it over the HF range?

Carl
KM1H

[K1ZJH]

can I offer one other suggestion?  Why not build the 1st mixer as as subassembly, such as on a small aluminum plate for example. Get the RX up and running using   a conventional mixer design, like a 6BY6, etc. Or, use a conventional mixer circuit borrowed  from a commercial RX, like the NC-300, etc.  Keep it simple and foolproof at first. When the entire receiver is working and debugged, you can go back and try different 1st mixers and go for optimum performance, if you so wish to...  I think Carl suggested subassemblies in a prior post. Not a bad way to go when winging it.

Pete

[K1ZJH]

There are others...  the 6JH8 and 6ME8 for starters.  Swan subbed the 7360s in their HF rigs for 6JH8s in later production runs.

Mea Cupla.  I meant to suggest the 6JH8... 

Pete

[N2DTS]

Maybe like this.

Lets see if it comes out right.

Not my work, but a very nice copy of my homebrew design...

Brett

[KI4YAN]

OK! chassis has been formed.

17" by 10" of 0.050" thick aluminum, 3" deep. Big enough to fit my dial assembly on, and conveniently it fits into a cabinet I made quite a while back.

[N2DTS]

Ok, maybe I am crazy.
I got a flex 5000a on Monday, and have been having fun with it, and last nite I decided to compare it to the homebrew receiver on AM, on 80 and 40 meters, using an antenna splitter and going into the same Marantz amplifier and big speaker.
I listened to short wave broadcast, and the AM window, weak signals and really strong signals, tested the extreme low frequency audio output of both (I have the flex limited to 20hz).

I thought the flex was supposed to be a good AM receiver, its listed 3rd on the Sherwood chart, and it does seem to work very well, and the sync detector does seem to work really well and help a lot on some signals.

But the homebrew sounds just as good, pulls out weak signals a little better?, seems to recover the audio off the carrier a little better (audio sounds louder for a given noise level).

Off frequency trash seems to be no problem on both receivers, at least within the bandwidth choices I have on the homebrew.

The results surprised me a lot, besides the band scope and sync detector, there is no improvement in the flex reception over the homebrew, and in some situations the homebrew is a bit clearer....

Maybe simple is better, or tubes are better then chips/software?

Brett

[KM1H]

A controlled sensitivity test should tell you a lot. Plus sound cards play a big part.

Ive the benefit of a HP-4970A NF meter and can select my take-off points anywhere in the RF/IF chain to locate trouble areas.

My much modified 75A4 will outhear any SS Ive ever compared it with.

Carl
KM1H

[N2DTS]

The flex 5000 does not use any sound card, that was the 1000.
Yes, I should get some real test equipment...

Brett

[KD6VXI]

The flex 5000 does not use any sound card, that was the 1000.
Yes, I should get some real test equipment...

Brett

It has a soundcard, it's just embedded in the equipment you bought.

I'd hesitate to say, it's probably one of the 'more compatible' with the flex software, though.

--Shane

[N2DTS]

I dont think so, since the output of the flex is a 400mb firewire interface.

Anyway, I figured out what the difference is:
One the homebrew, say someone puts on a carrier, it quiets the receiver, it does not need much carrier to quiet it.
On the flex 5000, a carrier does NOT quiet the receiver at all.
I think its the way the agc works, or how they detect AM, but when someone pauses in their speech, the band noise is there like there was no signal....

Brett

[w3jn]

LO phase noise from the DDS

[N2DTS]

No, its not that. phaze noise is not that bad, plus, phaze noise does not sound like qrm and static crashes...

Anyone else notice this?

I have compaired it a bunch of times, with a carrier, the normal receiver is quiet, the flex is not.
I dont remember the sdr-iq doing this.....

Brett

[KI4YAN]

I'm having an issue getting the dial strung correctly, and need some dial cord. Does anyone here have any sources for the good, non-stretching, woven nylon stuff?

[KM1H]

RadioDaze, AES, and probably others.

Carl
KM1H

[WU2D]

20 pound Backing for fly fishing line and even ice fishing line are good substitutes. You probably need a few lures and worms anyway.

Mike WU2D

[KI4YAN]

Power supply mounted up last night. 250V B+, regulated down to 150V for the non-audio sections. Everything checks out good, I have 200mA of B+ current and 3A of heater current, at 6.3V. I wound the power transformer for another project, but it looks like it'll do fine here.