Friday, October 15, 2010

HW-7 Versus HW-8 a Subjective Face off

HW-8 Versus HW-7 
HW 7 Top, HW 8 Bottom

HW 8 Transmit Test with WM-2

Back at the end of '08 I purchased both a HW-7 and a HW-8 to compare the DC receivers to the Willamette20 that I was constructing at the time.  I had tried them briefly but not head to head.  The HW-8 is going to be traded so before packing it up I thought I would test it for the next person and then I decided to put the HW-7 on the test as well.

These are some very unscientific findings based on yesterday's test.  The test setup included a Cuschcraft R7 vertical which is more or less tuned to CW frequencies, an Oak Hills QRP wattmeter and a Heath IP-18 regulated supply which is only rated at 500 ma so may not really be quite large enough.

The differences in the rigs include the the addition of 80M in the '8' in exchange for the crystal option on the '7'.  The other main differences are improvements in the receiver which manifest themselves as increased sensitivity and less microphonics on the '8'  There is also improved resistance to broadcast interference.  I owned an original HW-7 in 1972 or so that I built and used fairly often for several years and don't remember the broadcast interference but then again I usually used indoor dipoles tuned for one band rather than the R7 multiband vertical.
Anyway by careful tuning of the preselector knob I could still get readable signals with the '7' but it does not have the sensitivity of the '8' which has an RF Gain control.  The '7' though actually had a nicer CW 'note' (IMHO) than the '8' though with a good signal tuned in.  The sidetone however sounds much cleaner on the '8' vs a rather harsh sounding sidetone on the '7'.

On the transmit side I found both units to put out about 1 watt with the '7' being somewhat higher on all three of its bands.  The '8' put out just at 1 watt on 80M and then a bit less on 40M then a bit less on 20 and maybe 750mw on 15.  The '7' was over 1 watt on all bands.  This could be a result of weak p/s or individual tuning.

I have made maybe 50 or so QSO's with the Willamette20 now and it is a much better rig in some ways on 20M but of course you don't have the multiband option of the '7' or '8'.  The receiver in the Willamette20 is better than the '7' for sure and it sounds better than the '8' audio wise.  The tuning on the '20' is different because it uses a variactor diode instead of a capacitor.  The 10 turn potentiometer on the '20' makes for a nice although not linear tuning rate.  The HW's have a more linear tuning rate and a calibrated dial that is actually fairly accurate although not in the way we are now used to with modern radios.

Either of the Heaths will net you plenty of QSO's at the one watt QRP level but the '8''s receiver is overall better in sensitivity and resistance to  Short Wave B/C interference.

The single Band Willamette20 is at least equal and probably better than the '8' in the number of signals it will hear.  The 20 has a beautiful sounding sidetone and very smooth all solid state semi break in as well as a relatively hefty 4.5 watt output.

HW - 7 Story

In 1972 I purchased one of the 1st hundred or two HW-7's I ordered it new as soon as Heath was taking orders.  I lived in NC and built the rig and took it with me when I joined the Air Force in 1972.  Using a 15M dipole with 'clip lead extenders' taped to the WWII style barracks at Lowery AFB in Denver CO I made many contacts all over the world with the little rig.  Later on living 'off base' in a small house I was able to put a dipole up in the yard and continued to make contacts for several years.  This was my 1st QRP rig and getting another one was a trip down memory lane.  Later when the HW 8 came out I had been happy enough with the HW 7 that I did not think it would be worth buying another kit.  Well it is a step up as far as  the RX but I think I will keep the '7' 'just because'.

Another HW-8 on the way.

Links of lots of info Thanks to William Mcfadden WD8RIF
Good link to lots of HW-7 info
Good link to lots of HW-8 info

No comments: