Jan,
As you know, a ham's choice of
radio is even more controversial than a sailor's choice of anchors!!
And, the specific application that you're using the
radio for, will invariably play a
large part in what radio would
work best for you...
So, while I can give you a honest comparison of the two different radios' specs, and recommend one vs. the other, there might be others who will make an opposite recommendation for various applications (comparing the same specs..)
{I'm going to assume that your application is primarily HF ham voice/SSB
communications...and yes, you can improve on your 897, with a modest investment ($1000 or less)...
But, if your application is primarily CW (especially CW contesting), then you will need to spend much more $$$$ to get acceptable CW-contesting performance...
The problem is the close-in spec of most modern radios just isn't up-to-the-task....
For some explanations of the above, have a look at Rob Sherwood's presentations / seminars / white papers...
Sherwood Engineering Inc. (SEI)
Enjoy...}
1) First off, if you are actually experiencing receiver overload (de-sense and/or cross-mod) from signals well outside your passband, say 20khz - 50khz (or more) away from your frequency, when on-board with a simple random-length vertical, then I have a few quick thoughts
before we even get into what radio is better than another...
Quote:
Originally Posted by Goudurix
I am currently using a Yaesu FT 897D, SGC-230 ATU and sloping alternate backstay antenna on my sailing boat.
The FT-897 is really very sturdy, a versatile little workhorse but its receiver is easily overloaded and noisy.
I can now pick up a used Icom ic7000 at a good price. It is reputed to have a good to very good receiver for its price, with IF-DSP, digital filters. |
a) Make sure that you have the "pre-amp" turned OFF....(or in Yaesu's terminology, turn ON / activate the "IPO").....there should be no need for the pre-amp on the HF bands...
b) Make sure you have the
Noise Blanker (NB) turned OFF.....(I can count on my fingers of one hand, the number of radios whose
noise blankers do not adversely effect their rec dynamic range, both blocking/overload DR and IMD DR)
Noise blankers usually are effectively used just for "impulse noise", of which there is none at sea, and little on-board, so use of noise blanker is typically not necessary on-board...
c) Adjust the RF Gain down when you can (and turn volume/AF up as needed)
d) Use the attenuator (ATT) when you can, as well...as this will drop all signals (and noise) by about 10db, and further reduce overloading issues...
If, after doing these things/adjustments, you still have "overloading", please give more specifics....as you may have a receiver issue...
2) If you're having receiver IMD issues, not actual "overload", but reciprocal-mixing IMD products and non-linearities, generated inside your receiver, caused by
strong stations near your passband mixing with
your receiver's internal oscillator's noise.....then the above 4 things/adjustments also should improve the situation (as would
buying a radio with better overload and IMD specs..)
But, you may be finding
your receiver effected by
others transmitters poor spectral purity (transmitted noise, NOT "splatter")....
This is a getting to be a
real big problem on the HF ham bands these days, as more and more hams are using poorer and poorer transmitters, from which the transmitted noise causes receiver problems in others receivers outside the receiver's passband....(the transmitted noise mixes with your receiver's noise and the signals you're receiving, and causes rapid rises in non-linear responses/products in your receiver...)
{You see why I'm such a forceful opponent of using ham radios on the marine bands!!!}
Please note that this is NOT "splatter" that you hear from other stations, who are using transmitters with poor IMD specs and/or running them in a non-linear region (overdriving the modulator circuits, using ALC-based speech processing, increasing RF Drive levels / bypassing PA ALC systems, overdriving external PA's, etc. etc. etc...)
(I assume if you were having issues with splatter, you'd have mentioned that...)
3) Now onto some FT-897 vs. IC-7000 receiver specifics....
a) The FT-897 doesn't have the best oscil phase noise and its noise-limited close-in receive IMD tests and transmitted IMD products show this.....
So, in general the IC-7000 has better overall oscillator phase noise and less issues with reciprocal mixing products....
b) Comparing the exact specs, show the 7000 has a slight advantage (3db) in Blocking DR at 20khz, and a disadvantage of 8db at close-in (5khz) receive IMD tests...although the FT-897's close-in tests were noise-limited (which is borne out by your mention of it being a "noisy" receiver...)
c) And, in IMD3 testing, the IC-7000 and FT-897 are about equal (withn one db) at 20khz spacing, but at narrower 5khz spacing the IC-7000 shows an advantage of 10db - 12db...
So, on the surface, the IC-7000's receiver does have an advantage over the FT-897....but, not overwhelmingly dramatic...
4) Not sure what price you were considering paying for a new-to-you radio...but, you could do better than the IC-7000, the above minor advantages notwithstanding....(BTW, "IF-DSP" is not a cure-all for poor radio design / poor oscillator design....and even though the 7000 is better than the 897,
it isn't that much better...)
And, once you add in the other issues that you highlight...
Quote:
Originally Posted by Goudurix
However I also read about persistent issues:
- running warm on RX and hot or failure on transmit...
- very sensitive to feed voltage it needs 13,6V....the 12,6V of my gel house bank will easily go down to 12V on full power transmit at 20 Amps.
Any experiences?
Should I go for the ic-7000 to replace the FT897D and install also a voltage booster to keep about 13,6V?
BTW I tested the FT897D on the bench with my Diamond GSV3000 PSU and dummy load.
PEP power remains about 90 watts from 13,8V down to 12,0V.....
The FT897 doesn't seems to suffer from "mobile" power conditions from batteries. |
You may be trading one or two
current problems, for one or two NEW problems!!!
{And, Jan, please understand that while the 897 might still show 90 watts output on a meter, @ 12vdc, the transmit purity and transmit IMD at that lower voltage is truly horrible!!!
Heck, even at 13.8vdc, the 897's transmit IMD specs are pretty bad...
From the ARRL product review:
"Spectral display of the FT-897 transmitter during two-tone intermodulation distortion (IMD) testing on HF. Third order product is approximately 23 dB below PEP output, and the worst-case fifth-order product is approximately 37 dB down. The transmitter was being operated at 100 W output."
And, higher-order products (7th, 9th, 11th, and 13th) all plateauing at - 48 to - 50db....
Sorry to say, but it is transmitters like the 897 that contribute to the problems of others on-the-air....
}
5) And further, to be blunt.....
Why not simply look for a used Icom M-700Pro???
I just saw one on e-bay, sell for $550 USD, with a 30-day warranty....
It has an excellent receiver, which is almost impossible to overload...and one of the best HF transmitters made in the past 40 years!!!
It has an easy-to-use VFO-mode and makes an excellent HF ham radio, and although does not have
DSC, it is still a very good HF
Marine radio!!
6) Finally, to sum-up....
-- The IC-7000's receiver IS better than the FT897's..and you would probably find it better overall than the 897....
[and, the IC-7000's transmit IMD is much better, with 3rd at -33db; 5th at - 50db; 7th at -57db; 9th at -58db, and plateauing....]
-- If you make the 4 changes / adjustments to your 897, that I highlighted above (#1, a thru d), and still find the 897 to be unacceptable for your application...
Then, yes you'd probably find the IC-7000 to
work better for you...
(To be clear, I've used a 7000, and while it isn't a
bad radio, it's not really what I'd recommend...)
-- The added
issues (your mentioning of the 7000's warm/hot operating temps, and its low-voltage transmit cut-out) would be a problem for most....and here again, I'd recommend looking for a used M-700Pro....
FYI, you can see some radio
reviews / specs here:
The page you're trying to view is for members only.
Receiver Test Data
https://comm.capnhq.gov/comm/equipme...ent.cfm?type=a
https://comm.capnhq.gov/comm/equipme...ent.cfm?type=c
And, have a look at this thread as well...
http://www.cruisersforum.com/forums/...sb-115358.html
Jan, I know I didn't give you a clear-cut,
YES or
NO....
But, I do hope this helps...
73,
John, KA4WJA
s/v Annie Laurie
Linear Mode
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